GridFeatureSource¶
Namespace: ThinkGeo.Core
Reads cell data from a grid file and displays them in appropriate colors based on their values.
public class GridFeatureSource : FeatureSource
Inheritance Object → FeatureSource → GridFeatureSource
Remarks:
The GridFeatureSource displays cells with different colors in a rectangle area of map. The color of a cell depends on the cell value in the grid file. The grid file provides information about the grid, such as rows and columns number, cordinate of lower left corner, cell size, and values of cells.
Properties¶
PathFilename¶
This property gets and sets the path and file of the grid file you want to use.
public string PathFilename { get; set; }
Property Value¶
Remarks:
When you specify the path and file name it should be in the correct format. If the path and filename you provided we cannot find it then we will throw an exception.
CellSize¶
Gets the cell size of the grid.
public double CellSize { get; }
Property Value¶
NumberOfColumns¶
Gets column number of the grid.
public int NumberOfColumns { get; }
Property Value¶
NumberOfRows¶
Gets row number of the grid.
public int NumberOfRows { get; }
Property Value¶
LowerLeftPoint¶
Gets LowerLeft PointShape of the grid.
public PointShape LowerLeftPoint { get; }
Property Value¶
NoDataValue¶
Gets the NoDataValue in the grid.
public double NoDataValue { get; }
Property Value¶
IsEditable¶
This property returns if the FeatureSource allows edits or is read only.
public bool IsEditable { get; }
Property Value¶
Remarks:
This property is useful to check if a specific FeatureSource accepts editing. If you call the BeginTransaction and this property is false then an exception will be raised.
For developers who are creating or extending a FeatureSource it is expected that you override this virtual method if the new FeatureSource you are creating allows edits. By default the decimalDegreesValue if false meaning that if you want to allow edits you must override this method and return true.
DataValueColumnName¶
public string DataValueColumnName { get; }
Property Value¶
Id¶
public string Id { get; }
Property Value¶
CanExecuteSqlQuery¶
This property specifies whether the FeatureSource can excute a SQL query or not. If it is false, then it will throw exception when these APIs are calleds: ExecuteScalar, ExecuteNonQuery, ExecuteQuery
public bool CanExecuteSqlQuery { get; }
Property Value¶
Remarks:
The default implementation is false.
IsOpen¶
This property returns true if the FeatureSource is open and false if it is not.
public bool IsOpen { get; }
Property Value¶
Remarks:
Various methods on the FeatureSource require that it be in an open state. If one of those methods is called when the state is not open, then the method will throw an exception. To enter the open state, you must call the FeatureSource's Open method. The method will raise an exception if the current FeatureSource is already open.
Projection¶
public Projection Projection { get; protected set; }
Property Value¶
CanModifyColumnStructure¶
public bool CanModifyColumnStructure { get; }
Property Value¶
IsInTransaction¶
This property returns true if the FeatureSource is in a transaction and false if it is not.
public bool IsInTransaction { get; }
Property Value¶
Remarks:
To enter a transaction, you must first call the BeginTransaction method of the FeatureSource. It is possible that some FeatureSources are read-only and do not allow edits. To end a transaction, you must either call CommitTransaction or RollbackTransaction.
IsTransactionLive¶
This property returns true if the features currently modified in a transaction are expected to reflect their state when calling other methods on the FeatureSource, such as spatial queries.
public bool IsTransactionLive { get; set; }
Property Value¶
Remarks:
The live transaction concept means that all of the modifications you perform during a transaction are live from the standpoint of the querying methods on the object.
As an example, imagine that you have a FeatureSource that has 10 records in it. Next, you begin a transaction and then call GetAllFeatures. The result would be 10 records. After that, you call a delete on one of the records and call the GetAllFeatures again. This time you only get nine records, even though the transaction has not yet been committed. In the same sense, you could have added a new record or modified an existing one and those changes would be considered live, though not committed.
In the case where you modify records -- such as expanding the size of a polygon -- those changes are reflected as well. For example, you expand a polygon by doubling its size and then do a spatial query that would not normally return the smaller record, but instead would return the larger records. In this case, the larger records are returned. You can set this property to be false, as well; in which case, all of the spatially related methods would ignore anything that is currently in the transaction buffer waiting to be committed. In such a case, only after committing the transaction would the FeatureSource reflect the changes.
ProjectionConverter¶
This property holds the projection object that is used within the FeatureSource to ensure that features inside of the FeatureSource are projected.
public ProjectionConverter ProjectionConverter { get; set; }
Property Value¶
Remarks:
By default this property is null, meaning that the data being passed back from any methods on the FeatureSource will be in the coordinate system of the raw data. When you specify a projection object in the property, all incoming and outgoing method calls will subject the features to projection.
For example, if the spatial database you are using has all of its data stored in decimal degrees, but you want to see the data in UTM, you would create a projection object that goes from decimal degrees to UTM and set that as the projection. With this one property set, we will ensure that it will seem to you the developer that all of the data in the FeatureSource is in UTM. That means every spatial query will return UTM projected shapes. You can even pass in UTM shapes for the parameters. Internally, we will ensure that the shapes are converted to and from the projection without any intervention on the developer's part.
In fact, even when you override virtual or abstract core methods in the FeatureSource, you will not need to know about projections at all. Simply work with the data in its native coordinate system. We will handle all of the projection at the high level method.
GeoCache¶
The cache system.
public FeatureCache GeoCache { get; set; }
Property Value¶
Remarks:
You must set IsActive to true for the Cache system. The default is not active.
FeatureIdsToExclude¶
A collection of strings representing record id of features not to get in the Layer.
public Collection<string> FeatureIdsToExclude { get; }
Property Value¶
Remarks:
This string collection is a handy place to specify what records not to get from the source. Suppose you have a shape file of roads and you want to hide the roads within a particular rectangle, simply execute GetFeaturesInsideBoundingBox() and add the id of the return features to the collection and forget about them. Since you can set this by Layer it makes is easy to determine what to and what not to.
TransactionBuffer¶
The TransactionBuffer used in the Transaction System.
public TransactionBuffer TransactionBuffer { get; set; }
Property Value¶
Remarks:
The Transaction System
The transaction system of a FeatureSource sits on top of the inherited implementation of any specific source, such as Oracle Spatial or Shape files. In this way, it functions the same way for every FeatureSource. You start by calling BeginTransaction. This allocates a collection of in-memory change buffers that are used to store changes until you commit the transaction. So, for example, when you call the Add, Delete or Update method, the changes to the feature are stored in memory only. If for any reason you choose to abandon the transaction, you can call RollbackTransaction at any time and the in-memory buffer will be deleted and the changes will be lost. When you are ready to commit the transaction, you call CommitTransaction and the collections of changes are then passed to the CommitTransactionCore method and the implementer of the specific FeatureSource is responsible for integrating your changes into the underlying FeatureSource. By default the IsLiveTransaction property is set to false, which means that until you commit the changes, the FeatureSource API will not reflect any changes that are in the temporary editing buffer.
In the case where the IsLiveTransaction is set to true, then things function slightly differently. The live transaction concept means that all of the modifications you perform during a transaction are live from the standpoint of the querying methods on the object.
As an example, imagine that you have a FeatureSource that has 10 records in it. Next, you begin a transaction and then call GetAllFeatures. The result would be 10 records. After that, you call a delete on one of the records and call the GetAllFeatures again. This time you only get nine records, even though the transaction has not yet been committed. In the same sense, you could have added a new record or modified an existing one and those changes would be considered live, though not committed.
In the case where you modify records -- such as expanding the size of a polygon -- those changes are reflected as well. For example, you expand a polygon by doubling its size and then do a spatial query that would not normally return the smaller record, but instead would return the larger records. In this case, the larger records are returned. You can set this property to be false, as well; in which case, all of the spatially related methods would ignore anything that is currently in the transaction buffer waiting to be committed. In such a case, only after committing the transaction would the FeatureSource reflect the changes.
MaxRecordsToDraw¶
public int MaxRecordsToDraw { get; set; }
Property Value¶
Constructors¶
GridFeatureSource()¶
This is the constructor the for the class. If you use this constructor then you need to set the required properties manually.
public GridFeatureSource()
Remarks:
None
GridFeatureSource(String)¶
This is the class constructor.
public GridFeatureSource(string gridPathFilename)
Parameters¶
gridPathFilename String
This parameter represents the path and file name to the grid file.
Remarks:
None
Methods¶
OpenCore()¶
This method opens the FeatureSource so that it is initialized and ready to use.
protected void OpenCore()
Exceptions¶
InvalidOperationException
In the event you attempt to call this method on a feature source which has already been opened it will throw an InvalidOperationException.
Remarks:
This protected virtual method is called from the concreate public method Open. The open method play an important role as it is responsible for initializing the FeatureSource. Most methods on the FeatureSource will throw an exception if the state of the FeatureSource is not opened. When the map draws each layer it will open the FeatureSource as one of its first steps, then after it is finished drawing with that layer it will close it. In this way we are sure to release all resources used by the FeatureSource.
When implementing this virtual method consider opening files for file based source, connecting to databases in the database based sources and so on. You will get a chance to close these in the Close method of the FeatureSource.
OnStreamLoading(StreamLoadingEventArgs)¶
protected void OnStreamLoading(StreamLoadingEventArgs e)
Parameters¶
CloseCore()¶
This method closes the FeatureSource and releases any resources it was using.
protected void CloseCore()
Remarks:
This protected virtual method is called from the concreate public method Close. The close method plays an important role in the life cycle of the FeatureSource. It may be called after drawing to release any memory and other resources that were allocated since the Open method was called.
It is recommended that if you override this method that you take the following things into account. This method may be called multiple times so we suggest you write the so that that a call to a closed FeatureSource is ignored and does not generate an error. We also suggest that in the close you free all resources that have been opened. Remember that the object will not be destroyed but will be re-opened possibly in the near future.
GetColumnsCore()¶
This method returns the columns available for the FeatureSource.
protected Collection<FeatureSourceColumn> GetColumnsCore()
Returns¶
Collection<FeatureSourceColumn>
This method returns the columns available for the FeatureSource.
Exceptions¶
InvalidOperationException
In the event you attempt to call this method on a feature source which has not been opened it will throw an InvalidOperationException.
Remarks:
As this is the virtual core version of the Columns method it is intended to be overridden in inherited version of the class. When overriding you will be responsible for getting a list of all of the columns supported by the FeatureSource. In this way the FeatureSource will know what columns are available and will remove any extra columns when making calls to other core methods. For example if you have a FeatureSource that has three columns of information and the user calls a method and requests four columns of information, something they can do with custom fields, we will first compare what they are asking for to the results of the GetColumnsCore. In this way we can strip out custom columns before calling other Core methods which are only responsible for returning data in the FeatureSource. For more information on custom fields you can see the documentation on the OnCustomFieldsFetch.
CommitTransactionCore(TransactionBuffer)¶
This method will commit the existing transaction to its underlying source of data.
protected TransactionResult CommitTransactionCore(TransactionBuffer transactions)
Parameters¶
transactions TransactionBuffer
This parameter encapsulates all of the adds, edits and deleted that make up the
transaction. You will use this data to write the changes to your underlying data
source.
Returns¶
The return decimalDegreesValue of this method is a TransactionResult class which gives you the
status of the transaction you just committed. It includes how many of the updates,
adds, and deletes were successful and any error that were encountered during the
committing of the transaction.
Exceptions¶
InvalidOperationException
In the event you attempt to call this method on a feature source which is not in transaction it will throw an InvalidOperationException.
Remarks:
This method will commit the existing transaction to its underlying source of data. It will pass back the results of how the commit went to include any error received. If you are implementing your own FeatureSource then this is one of the crucial methods you must create. It should be fairly straight forward that you will loop through the transaction buffer and add, edit or delete the InternalFeatures in your underlying data source. Remember to build and pass back the TransactionResult class so that users of your FeatureSource can respond to failures you may encounter committing the InternalFeatures. We will handle the end of the transaction and also the cleanup of the transaction buffer. Your task will be to commit the records and produce a TransactionResult return.
The Transaction System
The transaction system of a FeatureSource sits on top of the inherited implementation of any specific source such as Oracle Spatial or Shape files. In this way it functions the same way for every FeatureSource. You start by calling the BeginTransaction. This allocates a collection of in memory change buffers that are used to store changes until you commit the transaction. So for example when you call the Add, Delete or Update method the changes to the feature are stored in memory only. If for any reason you choose to abandon the transaction you can call RollbackTransaction at any time and the in memory buffer will be deleted and the changes will be lost. When you are ready to commit the transaction you call the CommitTransaction and the collections of changes are then passed to the CommitTransactionCore method and the implementer of the specific FeatureSource is responsible for integrating your changes into the underlying FeatureSource. By default the IsLiveTransaction property is set to false which means that until you commit the changes the FeatureSource API will not reflect any changes that are in the temporary editing buffer.
In the case where the IsLiveTransaction is set to true then things function slightly differently. The live transaction concept means that all of the modification you perform during a transaction are live from the standpoint of the querying methods on the object.
To setup an example imagine that you have a FeatureSource that has 10 records in it. Next you begin a transaction and then call GetAllFeatures, the result would be 10 records. After that you call a delete on one of the records and call the GetAllFeatures again, this time you only get nine records. You receive nine records even though the transaction has not yet been committed. In the same sense you could have added a new record or modified an existing one and those changes are considered live though not committed.
In the case where you modify records such as expanding the size of a polygon those changes as well are reflected. So for example you expand a polygon by doubling its size and then do a spatial query that would not normally return the smaller record but would return the larger records, in this case the larger record is returned. You can set this property to be false as well in which case all of the spatial related methods would ignore anything that is currently in the transaction buffer waiting to be committed. In this case only after committing the transaction would the FeatureSource reflect the changes.
GetAllFeaturesCore(IEnumerable<String>)¶
This method returns all of the InternalFeatures in the FeatureSource.
protected Collection<Feature> GetAllFeaturesCore(IEnumerable<string> returningColumnNames)
Parameters¶
returningColumnNames IEnumerable<String>
This parameter allows you to select the field names of the column data you wish
to return with each Feature.
Returns¶
The return decimalDegreesValue is a collection of all of the InternalFeatures in the
FeatureSource.
Exceptions¶
InvalidOperationException
In the event you attempt to call this method on a feature source which has not been opened it will throw an InvalidOperationException.
Remarks:
This method returns all of the InternalFeatures in the FeatureSource. You will not need to consider anything about pending transactions as this will be handled in the non Core version of the method.
The main purpose of this method is to be the anchor of all of our default virtual implementations within this class. We wanted as the framework developers to provide you the user with as much default virtual implementation as possible. To do this we needed a way to get access to all of the features. For example, we want to create a default implementation for finding all of the InternalFeatures in a bounding box. Because this is an abstract class we do not know the specifics of the underlying data or how its spatial indexes work. What we do know is that if we get all the records then we can brute force the answer. In this way if you inherited form this class and only implemented this one method we can provide default implementations for virtually every other API.
While this is nice for you the developer if you decide to create your own FeatureSource it comes with a price. The price is that it is very inefficient. In the case we just discussed about finding all of the InternalFeatures in a bounding box we would not want to look at every record to fulfil this method. Instead we would want to override the GetFeaturesInsideBoundingBoxCore and implement specific code that would be fast. For example in Oracle Spatial there is a specific SQL statement to do this operation very quickly. The same holds true with other specific FeatureSource examples.
Most default implementations in the FeatureSource call the GetFeaturesInsideBoundingBoxCore which by default calls the GetAllFeaturesCore. It is our advice that if you create your own FeatureSource that you ALWAYS override the GetFeatureInsideBoundingBox. It will ensure that nearly every other API will operate efficiently. Please see the specific API to determine what method it uses.
GetBoundingBoxCore()¶
This method returns the bounding box which encompasses all of the features in the FeatureSource.
protected RectangleShape GetBoundingBoxCore()
Returns¶
This method returns the bounding box which encompasses all of the features in the
FeatureSource.
Exceptions¶
InvalidOperationException
If the operation is done under source closed state it will throw a InvalidOperationException.
Remarks:
This protected virtual method is called from the concreate public method GetBoundingBox. It does not take into account any transaction activity as this is the responsibility of the concreate public method GetBoundingBox. In this way as a developer if you choose to override this method you do not have to consider transaction at all.
The default implementation of GetBoundingBoxCore uses the GetAllRecordsCore method to calculate the bounding box of the FeatureSource. We strongly recommend that you provide your own implementation for this method that will be more efficient
If you do not override this method the means it gets the BoundingBox is by calling the GetAllFeatureCore method and deriving it from each feature. This is a very inefficient way to get the BoundingBox in most data sources. It is highly recommended that you override this method and replace it with a highly optimized version. For example in a ShapeFile the BoundingBox is in the main header of the file. Similarly if you are using Oracle Spatial you can execute a simple query to get the BoundingBox of all of the record without returning them. In these ways you can greatly improve the performance of this method.
GetCountCore()¶
This method returns the count of the number of records in this FeatureSource.
protected long GetCountCore()
Returns¶
This method returns the count of the number of records in this
FeatureSource.
Exceptions¶
InvalidOperationException
If the operation is done under source closed state it will throw a InvalidOperationException.
Remarks:
This protected virtual method is called from the concreate public method GetCount. It does not take into account any transaction activity as this is the responsibility of the concreate public method GetCount. In this way as a developer if you choose to override this method you do not have to consider transaction at all.
The default implementation of GetCountCore uses the GetAllRecordsCore method to calculate how many records there are in the FeatureSource. We strongly recommend that you provide your own implementation for this method that will be more efficient
If you do not override this method the means it gets the count is by calling the GetAllFeatureCore method and counting each feature. This is a very inefficient way to get the count in most data sources. It is highly recommended that you override this method and replace it with a highly optimized version. For example in a ShapeFile the record count is in the main header of the file. Similarly if you are using Oracle Spatial you can execute a simple query to get the count of all of the record without returning them. In these ways you can greatly improve the performance of this method.
GetFeaturesForDrawingCore(RectangleShape, Double, Double, IEnumerable<String>)¶
protected Collection<Feature> GetFeaturesForDrawingCore(RectangleShape boundingBox, double screenWidth, double screenHeight, IEnumerable<string> returningColumnNames)
Parameters¶
boundingBox RectangleShape
screenWidth Double
screenHeight Double
returningColumnNames IEnumerable<String>
Returns¶
GetFeaturesInsideBoundingBoxCore(RectangleShape, IEnumerable<String>)¶
This method returns all of the InternalFeatures of this FeatureSource inside of the specified bounding box.
protected Collection<Feature> GetFeaturesInsideBoundingBoxCore(RectangleShape boundingBox, IEnumerable<string> returningColumnNames)
Parameters¶
boundingBox RectangleShape
This parameter represents the bounding box you with to find InternalFeatures inside
of.
returningColumnNames IEnumerable<String>
This parameter allows you to select the field names of the column data you wish
to return with each Feature.
Returns¶
The return decimalDegreesValue is a collection of all of the InternalFeatures that are inside of the
bounding box.
Exceptions¶
InvalidOperationException
In the event you attempt to call this method on a feature source which has not been opened it will throw an InvalidOperationException.
ArgumentNullException
If you pass a null as the returningColumnNames we will throw an ArgumentNullException.
ArgumentNullException
If you pass a null as the boundingBox we will throw an ArgumentNullException.
Remarks:
This method returns all of the InternalFeatures of this FeatureSource inside of the specified bounding box. If you are overriding this method you will not need to consider anything about transactions as this is handled by the concreate version of this method.
The default implementation of GetFeaturesInsideBoundingBoxCore uses the GetAllRecordsCore method to determine which InternalFeatures are inside of the bounding box. We strongly recommend that you provide your own implementation for this method that will be more efficient. It is especially important for this method as many other default virtual methods use this for their calculations. We highly recommend when you override this method that you use any spatial indexes you have at your disposal to make this method as fast as possible.
GetFeatureIdsCore()¶
protected Collection<string> GetFeatureIdsCore()
Returns¶
GenerateGridMatrix(GridDefinition, GridInterpolationModel)¶
This method calculates all the cells in the grid and returns the result in the form of the GridCell matrix
public static GridCell[,] GenerateGridMatrix(GridDefinition gridDefinition, GridInterpolationModel gridInterpolationModel)
Parameters¶
gridDefinition GridDefinition
This parameter contains the properties used to describe the grid.
gridInterpolationModel GridInterpolationModel
This parameter represents the interpolation model for calculating cell value of the grid
Returns¶
GridCell[,]
This method returns the GridCell matrix which is calculated based on the input parameters.
GenerateGridMatrix()¶
This method generates the cell matrix based on NumberOfColumns and NumberOfRows of current grid.
public GridCell[,] GenerateGridMatrix()
Returns¶
GridCell[,]
This method returns a cell matrix of current grid.
ReplaceNoDataValue(GridCell[,], Double)¶
public static GridCell[,] ReplaceNoDataValue(GridCell[,] gridMatrix, double noDataValue)
Parameters¶
gridMatrix GridCell[,]
noDataValue Double
Returns¶
ReplaceNoDataValue(GridCell[,], Double, GridInterpolationModel)¶
public static GridCell[,] ReplaceNoDataValue(GridCell[,] gridMatrix, double noDataValue, GridInterpolationModel gridInterpolationModel)
Parameters¶
gridMatrix GridCell[,]
noDataValue Double
gridInterpolationModel GridInterpolationModel
Returns¶
GenerateGrid(GridDefinition, GridInterpolationModel, Stream, Func<Double, String>)¶
This method calculates all the cells in the grid and write the value of them into the grid file associates with the stream.
public static void GenerateGrid(GridDefinition gridDefinition, GridInterpolationModel gridInterpolationModel, Stream outputStream, Func<double, string> cellValueToStringFunc)
Parameters¶
gridDefinition GridDefinition
This parameter contains the parameters used to describe the grid.
gridInterpolationModel GridInterpolationModel
This parameter represents the interpolation model for calculating cell value of the grid
outputStream Stream
This parameter represents the stream associates with the output file.
cellValueToStringFunc Func<Double, String>
The function of converting the cell value from double to string. The converted string will be written to the grid stream. By default, it uses the expression cellValue.ToString(CultureInfo.InvariantCulture) to perform the conversion.
Exceptions¶
ArgumentNullException
If you pass a null as gridDefinition, there will be a ArgumentNullException thrown.
SaveGridsToStream(GridCell[,], Double, Stream, Func<Double, String>)¶
public static void SaveGridsToStream(GridCell[,] cells, double noDataValue, Stream outputStream, Func<double, string> cellValueToStringFunc)
Parameters¶
cells GridCell[,]
noDataValue Double
outputStream Stream
cellValueToStringFunc Func<Double, String>
SaveGridsToGrdFile(GridCell[,], Double, String, Func<Double, String>)¶
public static void SaveGridsToGrdFile(GridCell[,] cells, double noDataValue, string outputFilePath, Func<double, string> cellValueToStringFunc)
Parameters¶
cells GridCell[,]
noDataValue Double
outputFilePath String
cellValueToStringFunc Func<Double, String>
Events¶
GeneratingGrid¶
public static event EventHandler<GeneratingGridFeatureSourceEventArgs> GeneratingGrid;
StreamLoading¶
public event EventHandler<StreamLoadingEventArgs> StreamLoading;
DrawingProgressChanged¶
public event EventHandler<DrawingProgressChangedEventArgs> DrawingProgressChanged;
GettingColumns¶
public event EventHandler<GettingColumnsFeatureSourceEventArgs> GettingColumns;
GottenColumns¶
public event EventHandler<GottenColumnsFeatureSourceEventArgs> GottenColumns;
GettingFeaturesByIds¶
public event EventHandler<GettingFeaturesByIdsFeatureSourceEventArgs> GettingFeaturesByIds;
GettingFeaturesForDrawing¶
public event EventHandler<GettingFeaturesForDrawingFeatureSourceEventArgs> GettingFeaturesForDrawing;
CustomColumnFetch¶
This event is raised when fields are requested in a feature source method that do not exist in the feature source. It allows you to supplement the data from any outside source you have.
public event EventHandler<CustomColumnFetchEventArgs> CustomColumnFetch;
Remarks:
This event is raised when fields are requested in a feature source method that do not exist in the feature source. It allows you to supplement the data from any outside source you have.
It is used primarily when you have data relating to a particular feature or set of features that is not within source of the data. For example, you may have a shape file of the world whose .dbf component describes the area and population of each country. Additionally, in an outside SQL Server table, you may also have data about the countries, and it is this data that you wish to use for determining how you want to color each country.
To integrate this SQL data, you simply create a file name that does not exist in the .dbf file. Whenever Map Suite is queried to return records that specifically require this field, the FeatureSource will raise this event and allow you the developer to supply the data. In this way, you can query the SQL table and store the data in some sort of collection, and then when the event is raised, simply supply that data.
As this is an event, it will raise for each feature and field combination requested. This means that the event can be raised quite often, and we suggest that you cache the data you wish to supply in memory. We recommend against sending out a new SQL query each time this event is raised. Image that you are supplementing two columns and your query returns 2,000 rows. This means that if you requested those fields, the event would be raised 4,000 times.
CommittingTransaction¶
This event is raised after the CommitTransaction method is called, but before the CommitTransactionCore is called. This allows you access to the TransactionBuffer before the transaction is committed. It also allows you to cancel the pending commit of the transaction.
public event EventHandler<CommittingTransactionEventArgs> CommittingTransaction;
Remarks:
This event is raised before the CommitTransactionCore is called and allows you access to the TransactionBuffer before the transaction is committed. It also allows you to cancel the pending transaction. The TransactionBuffer is the object that stores all of the pending transactions and is accessible through this event to allow you to either add, remove or modify transactions.
In the event that you cancel the CommitTransaction method, the transaction remains intact and you will still be editing. This makes it a nice place to possibly check for connectivity before the TransactionCore code is run, which is where the records are actually committed. Calling the RollBackTransaction method is the only way to permanently cancel a pending transaction without committing it.
CommittedTransaction¶
This event is raised after the CommitTransaction and the CommitTransactionCore are called and allows you access to the TransactionBuffer and the TransactionResults object before CommitTransaction method is returned.
public event EventHandler<CommittedTransactionEventArgs> CommittedTransaction;
Remarks:
This event is raised after the CommitTransactionCore is called and allows you access to the TransactionBuffer and the TransactionResults object before CommitTransaction method is returned.
With this event, you can analyse the results of the transaction and do any cleanup code necessary. In the event some of the records did not commit, you can handle those items here. The TransactionResults object is passed out of the CommitTransaction method so you could analyze it then; however, this is the only place where you have access to both the TransactionResults object and the TransactionBuffer object at the same time. These are useful together to try and determine what went wrong and possibly try and re-commit them.
At the time of this event you will technically be out of the current transaction.
OpeningFeatureSource¶
This event is called before the opening of the FeatureSource.
public event EventHandler<OpeningFeatureSourceEventArgs> OpeningFeatureSource;
Remarks:
This event is called before the opening of the FeatureSource. Technically, this event is called after the calling of the Open method on the FeatureSource, but before the protected OpenCore method.
It is typical that the FeatureSource may be opened and closed may times during the life cycle of your application. The type of control the MapEngine is embedded in will dictate how often this happens. For example, in the case of the Web Edition, each time a FeatureSource is in the Ajax or Post Back part of the page cycle, it will close the FeatureSource before returning back to the client. This is to conserve resources, as the web is a connection-less environment. In the case of the Desktop Edition, we can keep the FeaureSources open, knowing that we can maintain a persistent connection.
OpenedFeatureSource¶
This event is called after the opening of the FeatureSource.
public event EventHandler<OpenedFeatureSourceEventArgs> OpenedFeatureSource;
Remarks:
This event is called after the opening of the FeatureSource. Technically, this event is called after the calling of the Open method on the FeatureSource and after the protected OpenCore method is called.
It is typical that the FeatureSource may be opened and closed may times during the life cycle of your application. The type of control the MapEngine is embedded in will dictate how often this happens. For example, in the case of the Web Edition, each time a FeatureSource is in the Ajax or Post Back part of the page cycle, it will close the FeatureSource before returning back to the client. This is to conserve resources, as the web is a connection-less environment. In the case of the Desktop Edition, we can keep the FeaureSources open, knowing that we can maintain a persistent connection.
ClosingFeatureSource¶
This event is called before the closing of the FeatureSource.
public event EventHandler<ClosingFeatureSourceEventArgs> ClosingFeatureSource;
Remarks:
This event is called before the closing of the FeatureSource. Technically, this event is called after the calling of the Close method on the FeatureSource, but before the protected CloseCore method.
It is typical that the FeatureSource may be opened and closed may times during the life cycle of your application. The type of control the MapEngine is embedded in will dictate how often this happens. For example, in the case of the Web Edition, each time a FeatureSource is in the Ajax or Post Back part of the page cycle, it will close the FeatureSource before returning back to the client. This is to conserve resources, as the web is a connection-less environment. In the case of the Desktop Edition, we can keep the FeaureSources open, knowing that we can maintain a persistent connection.
ClosedFeatureSource¶
This event is called after the closing of the FeatureSource.
public event EventHandler<ClosedFeatureSourceEventArgs> ClosedFeatureSource;
Remarks:
This event is called after the closing of the FeatureSource. Technically, this event is called after the calling of the Close method on the FeatureSource and after the protected CloseCore method.
It is typical that the FeatureSource may be opened and closed may times during the life cycle of your application. The type of control the MapEngine is embedded in will dictate how often this happens. For example, in the case of the Web Edition, each time a FeatureSource is in the Ajax or Post Back part of the page cycle, it will close the FeatureSource before returning back to the client. This is to conserve resources, as the web is a connection-less environment. In the case of the Desktop Edition, we can keep the FeaureSources open, knowing that we can maintain a persistent connection.