Writing .NET code using properties

• About writing .NET code using properties
• Property types
  • Property Get
  • Property Put
  • Property Get/Put
  • Property Put by reference
  • Property Get/Put by reference
• Coding caveats
  • VB .NET code
  • C# code

Interface key	Property type
	Property Get
	Property Put
	Property Get/Put
	Property Put by reference
	Property Get/Put by reference

• Property Get
• Property Put
• Property Get/Put
• Property Put by reference
• Property Get/Put by reference

The Property Get () means you can only retrieve the value of that property (that is, it is read-only). Its data type is by value (ByVal). IField.AliasName is an example of a Property Get (read-only) type. See the following screen shot:

Public Class Class1
    
    Public Sub Test()
        
        ' Create a new field object.
        Dim field As IField=New FieldClass
        
        ' The following is the appropriate use of the Property Get:
        Dim myString As System.String=field.AliasName
        
        ' The following is an inappropriate use of the Property Get:
        ' The code will not compile and returns the following error message:
        ' Property 'AliasName' is 'ReadOnly.'
        field.AliasName="Won't Work - Write Only Property"
        
    End Sub
    
End Class

public class Class1
{

    public void test()
    {

        // Create a new field object.
        IField field=new FieldClass();

        // The following is the appropriate use of the Property Get:
        System.String myString=field.AliasName;

        // The following is an inappropriate use of the Property Get:
        // The code will not compile and returns the following error message:
        // Property or indexer 'ESRI.ArcGIS.Geodatabase.IField.AliasName' cannot be assigned to; it is read-only.
        field.AliasName="Won't Work - Write Only Property";
    }

}

The Property Put or Set () means that you can only set the value of that property (that is, it is write-only). Its data type is by value (ByVal). IFieldEdit.AliasName is an example of a Property Put (write-only) type. See the following screen shot:

Public Class Class1
    
    Public Sub Test()
        
        ' Create a new field object.
        Dim field As IField=New FieldClass
        
        ' Create a fieldEdit object from the field object.
        Dim fieldEdit As IFieldEdit=CType(field, IFieldEdit)
        
        ' The following is the appropriate use of the Property Put (or Set):
        fieldEdit.AliasName_2="My Write Only Name"
        
        ' The following is an inappropriate use of the Property Put (or Set):
        ' The code will not compile and returns the following error message:
        ' Property 'AliasName_2' is 'WriteOnly.'
        Dim myString As System.String=fieldEdit.AliasName_2
        
    End Sub
    
End Class

public class Class1
{

    public void test()
    {
        // Create a new field object.
        IField field=new FieldClass();

        // Create a fieldEdit object from the field object.
        IFieldEdit fieldEdit=(IFieldEdit)field;

        // The following is the appropriate use of the Property Put (or Set):
        fieldEdit.AliasName_2="My Write Only Name";

        // The following is an inappropriate use of the Property Put (or Set):
        // The code will not compile and returns the following error message:
        // The property or indexer 'ESRI.ArcGIS.Geodatabase.IFieldEdit.AliasName_2' cannot be used in this context because it lacks the get accessor.
        System.String myString=fieldEdit.AliasName_2;
    }

}

The Property Get/Put () means that you can retrieve and set the value of that property (that is, it is read/write). Both properties data type is by value (ByVal). IEnvelope.Depth is an example of a Property Get/Put (read/write) type. See the following screen shot:

Public Class Class1
    
    Public Sub Test()
        
        ' Create a new envelope object.
        Dim envelope As IEnvelope=New EnvelopeClass
        
        ' The following is the appropriate use of the Property Put (or Set):
        envelope.Depth=25
        
        ' The following is the appropriate use of the Property Get:
        Dim myDouble As System.Double=envelope.Depth
        
    End Sub
    
End Class

public class Class1
{

    public void test()
    {
        // Create a new envelope object.
        IEnvelope envelope=new EnvelopeClass();

        // The following is the appropriate use of the Property Put (or Set):
        envelope.Depth=25;

        // The following is the appropriate use of the Property Get:
        System.Double myDouble=envelope.Depth;
    }

}

Property Put or Set () by reference means you can only set the value of that property (that is, it is write-only). It uses the same style of .NET syntax as the Property Put. Additional insight can be gained by understanding the graphical representation on the interface page in conjunction with using the syntax usage of the property page.

See the following code example showing how to use the Property Put by reference:

Public Class Class1
    
    Public Sub Test(ByVal activeView As ESRI.ArcGIS.Carto.IActiveView)
        
        ' Create a newEnvelopeFeedback object.
        Dim newEnvelopeFeedback As INewEnvelopeFeedback=New NewEnvelopeFeedback
        
        ' Use the Property Put or Set to set the newEnvelopeFeedback object's
        ' .Display property by reference.
        newEnvelopeFeedback.Display=activeView.ScreenDisplay
        
        ' The following is an inappropriate use of the Property Put or Set (it is write-only):
        ' The code will not compile and returns the following error:
        ' Property 'Display' is 'WriteOnly.'
        Dim display As IDisplay=newEnvelopeFeedback.Display
        
    End Sub
    
End Class

public class Class1
{

    public void test(ESRI.ArcGIS.Carto.IActiveView activeView)
    {
        // Create a newEnvelopeFeedback object.
        INewEnvelopeFeedback newEnvelopeFeedback=new NewEnvelopeFeedback();

        // Use the Property Put or Set to set the newEnvelopeFeedback object's
        // .Display property by reference.
        newEnvelopeFeedback.Display=activeView.ScreenDisplay;

        // The following is an inappropriate use of the Property Put or Set (it is write-only):
        // The code will not compile and returns the following error:
        // The property or indexer 'ESRI.ArcGIS.Display.INewEnvelopeFeedback.Display' cannot be used in this context because it lacks the get accessor.
        IDisplay display=newEnvelopeFeedback.Display;
    }

}

The Property Get/Put or Get/Set () by reference means that you can retrieve and set the value of that property (it is read/write). It uses the same style of .NET syntax as the Property Get/Put. Additional insight can be gained by understanding the graphical representation on the interface page in conjunction with using the syntax usage of the property page.

Public Class Class1
    
    
    Public Sub Test()
        
        ' Create a test SpatialReference.
        Dim spatialReferenceFactory2 As ISpatialReferenceFactory2=New SpatialReferenceEnvironmentClass
        Dim spatialReference As ISpatialReference=spatialReferenceFactory2.CreateSpatialReference(esriSRProjCSType.esriSRProjCS_World_Robinson)
        
        ' Create a new point.
        Dim point As IPoint=New PointClass
        
        ' Put or Set by reference the SpatialReference of the point.
        point.SpatialReference=spatialReference
        System.Windows.Forms.MessageBox.Show(point.SpatialReference.Name) ' Displays "World Robinson"
        
        ' Create another SpatialReference from an existing SpatialReference of a point (Get) by value.
        Dim anotherSpatialReference As ISpatialReference=point.SpatialReference
        System.Windows.Forms.MessageBox.Show(anotherSpatialReference.Name) ' Displays "World Robinson."
        
        ' Create a third test SpatialReference (different from the original).
        Dim spatialReferenceFactory2_THIRD As ISpatialReferenceFactory2=New SpatialReferenceEnvironmentClass
        Dim spatialReference_THIRD As ISpatialReference=spatialReferenceFactory2_THIRD.CreateSpatialReference(esriSRProjCSType.esriSRProjCS_World_Sinusoidal)
        
        ' Since you perform a Put or Set by reference, the name changes.
        point.SpatialReference=spatialReference_THIRD
        System.Windows.Forms.MessageBox.Show(point.SpatialReference.Name) ' Displays "World Sinusoidal."
        
        ' AnotherSpatialReference was originally created from point.SpatialReference, but
        ' it was done using by value and therefore, retains its original value.
        System.Windows.Forms.MessageBox.Show(anotherSpatialReference.Name) ' Still displays "World Robinson."
        
    End Sub
    
End Class

public class Class1
{

    public void test()
    {
        // Create a test SpatialReference.
        ISpatialReferenceFactory2 spatialReferenceFactory2=new
            SpatialReferenceEnvironmentClass();
        ISpatialReference spatialReference =
            spatialReferenceFactory2.CreateSpatialReference((int)
            esriSRProjCSType.esriSRProjCS_World_Robinson);

        // Create a new point.
        IPoint point=new PointClass();

        // Put or Set by reference the SpatialReference of the point.
        point.SpatialReference=spatialReference;
        System.Windows.Forms.MessageBox.Show(point.SpatialReference.Name); 
            // Displays "World Robinson."

        // Create another SpatialReference from an existing SpatialReference of a point (Get) by value.
        ISpatialReference anotherSpatialReference=point.SpatialReference;
        System.Windows.Forms.MessageBox.Show(anotherSpatialReference.Name); 
            // Displays "World Robinson."

        // Create a third test SpatialReference (different from the original).
        ISpatialReferenceFactory2 spatialReferenceFactory2_THIRD=new
            SpatialReferenceEnvironmentClass();
        ISpatialReference spatialReference_THIRD =
            spatialReferenceFactory2_THIRD.CreateSpatialReference((int)
            esriSRProjCSType.esriSRProjCS_World_Sinusoidal);

        // Since you performed a Put or Set by reference, the name changes.
        point.SpatialReference=spatialReference_THIRD;
        System.Windows.Forms.MessageBox.Show(point.SpatialReference.Name); 
            // Displays "World Sinusoidal."

        // AnotherSpatialReference was originally created from point.SpatialReference, but
        // it was done using by value and therefore, retains its original value.
        System.Windows.Forms.MessageBox.Show(anotherSpatialReference.Name); 
            // Still displays "World Robinson."
    }

}

Public Class Class1
    
    Public Sub Test(ByVal application As IApplication)
        
        ' Property Put (or Set).
        application.StatusBar.Message(0)="This is a message"
        
        'Property Get.
        Dim message As String=application.StatusBar.Message(0)
    End Sub
    
End Class

public class Class1
{

    public void test(IApplication application)
    {
        // Property Put (or Set).
        application.StatusBar.set_Message(0, "This is message");

        //Property Get.
        string message=application.StatusBar.get_Message(0);
    }

}

See Also:

• ESRI.ArcGIS.Geodatabase
• ESRI.ArcGIS.Geometry
• ESRI.ArcGIS.Display
• ESRI.ArcGIS.Framework