ValueStyle¶
Namespace: ThinkGeo.Core
This class allows you to match a value with data in the feature to determine how to draw that feature.
public class ValueStyle : Style
Inheritance Object → Style → ValueStyle
Remarks:
Value Style:
The ValueStyle allows you to match data in the FeatureSource against a value string. If the value matches, then we will use the style defined in that item to do the drawing. For example, let's say you have some data that contains states, and each state is categorized as either a high, medium or low pollution state. Based on the string values of "High", Medium" and "Low", we can match on these. If a feature's data for the column matched the string "High", then we would use the high ValueItem's styles to draw that feature. This can be applied to all kinds of things, such as road classifications, etc.
This can be somewhat slow because we have to match data from the FeatureSource. If performance is key, then instead of using the ValueStyle, we recommend that you create a set custom index for your layer, one index with only "High" elements, one for "Medium" and so on. Then load each as a separate layer. In this way, you would only have one data set, but multiple indexes. This is the fastest way if you are working with Shape Files. If you are working with spatial databases, then we suggest creating a view to segment out each category.
Properties¶
ColumnName¶
This property gets and sets the column name used to match with the value specified in the items.
public string ColumnName { get; set; }
Property Value¶
This property gets the column name used to match with the value specified in
the items.
Remarks:
This is the column we use for matching.
DrawingOrder¶
public ValueDrawingOrder DrawingOrder { get; set; }
Property Value¶
ValueItems¶
This property gets the collection of ValueItems. Each item can have its own value to match.
public Collection<ValueItem> ValueItems { get; }
Property Value¶
Collection<ValueItem>
This property gets the collection of ValueItems.
Remarks:
You will want to add ValueItems to this collection. Each item can have its own style and matching string.
Name¶
This property gets and set the name of the style.
public string Name { get; set; }
Property Value¶
String
This property gets the name of the style.
Remarks:
This name is not used by the system; it is only for the developer. However, it can be used if you generate your own legend.
IsActive¶
This property gets and sets the active status of the style.
public bool IsActive { get; set; }
Property Value¶
Boolean
This property gets the active status of the style.
Remarks:
If the style is not active then it will not draw.
RequiredColumnNames¶
This property gets the collection of fields that are required for the style.
public Collection<string> RequiredColumnNames { get; }
Property Value¶
This property gets the collection of fields that are required for the
style.
Remarks:
This property gets the collection of fields that are required for the style. These are in addition to any other columns you specify in styles that inherit from this one. For example, if you have use a ValueStyle and it requires a column name for the value comparison, then that column does not need to be in this collection. You only use the RequiredColumnNames for columns you need beyond those required by specific inherited styles.
Filters¶
public Collection<string> Filters { get; }
Property Value¶
Constructors¶
ValueStyle()¶
This is a constructor for the class.
public ValueStyle()
Remarks:
If you use this constructor, you need to set the required properties manually.
ValueStyle(String, Collection<ValueItem>)¶
This is a constructor for this class.
public ValueStyle(string columnName, Collection<ValueItem> valueItems)
Parameters¶
columnName String
The columnName used to match with the value specified in the items.
valueItems Collection<ValueItem>
The collection of ValueItems. Each item can have its own value to match.
Methods¶
DrawCore(IEnumerable<Feature>, GeoCanvas, Collection<SimpleCandidate>, Collection<SimpleCandidate>)¶
This method draws the features on the view you provided.
protected void DrawCore(IEnumerable<Feature> features, GeoCanvas canvas, Collection<SimpleCandidate> labelsInThisLayer, Collection<SimpleCandidate> labelsInAllLayers)
Parameters¶
features IEnumerable<Feature>
This parameter represents the features you want to draw on the view.
canvas GeoCanvas
This parameter represents the view you want to draw the features on.
labelsInThisLayer Collection<SimpleCandidate>
The labels will be drawn in the current layer only.
labelsInAllLayers Collection<SimpleCandidate>
The labels will be drawn in all layers.
Exceptions¶
InvalidOperationException
In the event you attempt to call this method when the GeoCanvas's IsDrawing mode is false, it will throw an InvalidOperationException.
ArgumentNullException
If you pass a null as the view, we will throw an ArgumentNullException.
ArgumentNullException
If you pass a null as the features, we will throw an ArgumentNullException.
ArgumentNullException
If columnName is null, we will throw an ArgumentNullException.
Remarks:
This overridden method is called from the concrete public method Draw. In this method, we take the features you passed in and draw them on the view you provided. Each style (based on its properties) may draw each feature differently.
When overriding this method, consider each feature and its column data values. You can use the full power of the GeoCanvas to do the drawing. If you need column data for a feature, be sure to override the GetRequiredColumnNamesCore and add the columns you need to the collection. In many of the styles, we add properties to allow the user to specify which field they need; then, in the GetRequiredColumnNamesCore, we read that property and add it to the collection.
GetRequiredColumnNamesCore()¶
This method returns the column data for each feature that is required for the style to properly draw.
protected Collection<string> GetRequiredColumnNamesCore()
Returns¶
Collection<String>
This method returns a collection of the column names that it needs.
Exceptions¶
ArgumentNullException
If columnName is null, we will throw an ArgumentNullException.
Remarks:
This abstract method is called from the concrete public method GetRequiredFieldNames. In this method, we return the column names that are required for the style to draw the feature properly. For example, if you have a style that colors areas blue when a certain column value is over 100, then you need to be sure you include that column name. This will ensure that the column data is returned to you in the feature when it is ready to draw.
In many of the styles, we add properties to allow the user to specify which field they need; then, in the GetRequiredColumnNamesCore, we read that property and add it to the collection.
DrawSampleCore(GeoCanvas, DrawingRectangleF)¶
protected void DrawSampleCore(GeoCanvas canvas, DrawingRectangleF drawingExtent)
Parameters¶
canvas GeoCanvas
drawingExtent DrawingRectangleF