BindingGroup.GetValue Method (Object, String)
Returns the proposed value for the specified property and item.
Assembly: PresentationFramework (in PresentationFramework.dll)
Parameters
- item
-
Type:
System.Object
The object that contains the specified property.
- propertyName
-
Type:
System.String
The property whose proposed value to get.
| Exception | Condition |
|---|---|
| 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
Available since 3.0