BindingGroup.GetValue Method (Object, String)

Returns the proposed value for the specified property and item.

Namespace:  System.Windows.Data
Assembly:  PresentationFramework (in PresentationFramework.dll)

'Declaration
Public Function GetValue ( _
	item As Object, _
	propertyName As String _
) As Object

Parameters

item
Type: System.Object

The object that contains the specified property.

propertyName
Type: System.String

The property whose proposed value to get.

Return Value

Type: System.Object
The proposed property value.

ExceptionCondition
InvalidOperationException

There is not a binding for the specified item and property.

ValueUnavailableException

The value of the specified property is not available, due to a conversion error or because an earlier validation rule failed.

Use this method in the ValidationRule.Validate method to get the value to be committed to the source. The type of the return value depends on the stage at which the ValidationRule occurs. For example, if a TextBox is data bound to a property of type integer and the ValidationRule that calls GetValue(Object, String) has its ValidationStep set to RawProposedValue, the method returns a string. If the ValidationRule has its ValidationStep set to ConvertedProposedValue, the method returns whatever type that is returned by the binding's converter. In this example, GetValue(Object, String) usually returns an integer.

The following example is part of an application that prompts the user to enter multiple customers and assign a sales representative to each customer. The application checks that the sales representative and the customer belong to the same region. The example shows the Validate method, which uses the GetValue(Object, String) method to get values that the customer entered.

	Public Class AreasMatch
		Inherits ValidationRule
		Public Overrides Function Validate(ByVal value As Object, ByVal cultureInfo As System.Globalization.CultureInfo) As ValidationResult
			Dim bg As BindingGroup = TryCast(value, BindingGroup)
			Dim cust As Customer = TryCast(bg.Items(0), Customer)

			If cust Is Nothing Then
				Return New ValidationResult(False, "Customer is not the source object")
			End If

			Dim region As Region = CType(bg.GetValue(cust, "Location"), Region)
			Dim rep As ServiceRep = TryCast(bg.GetValue(cust, "ServiceRepresentative"), ServiceRep)
			Dim customerName As String = TryCast(bg.GetValue(cust, "Name"), String)

			If region = rep.Area Then
				Return ValidationResult.ValidResult
			Else

				Dim sb As New StringBuilder()
				sb.AppendFormat("{0} must be assigned a sales representative that serves the {1} region. " & vbLf & " ", customerName, region)
				Return New ValidationResult(False, sb.ToString())
			End If
		End Function
	End Class

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5 SP1, 3.0 SP2

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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