BindingGroup.GetValue(Object, String) 方法

定义

命名空间:

System.Windows.Data

程序集:

PresentationFramework.dll

返回指定的属性和项的建议值。

public:
 System::Object ^ GetValue(System::Object ^ item, System::String ^ propertyName);

public object GetValue (object item, string propertyName);

override this.GetValue : obj * string -> obj

Public Function GetValue (item As Object, propertyName As String) As Object

参数

item

Object

包含指定属性的对象。

propertyName

String

要获取其建议值的属性。

返回

Object

建议的属性值。

例外

InvalidOperationException

指定项和属性之间没有绑定。

ValueUnavailableException

由于转换错误或早期验证规则失败，指定的属性值不可用。

示例

以下示例是提示用户输入多个客户并将销售代表分配给每个客户的应用程序的一部分。 应用程序会检查销售代表和客户是否属于同一区域。 该示例显示 Validate 该方法，该方法使用 GetValue(Object, String) 该方法获取客户输入的值。

public class AreasMatch : ValidationRule
{
    public override ValidationResult Validate(object value, System.Globalization.CultureInfo cultureInfo)
    {
        BindingGroup bg = value as BindingGroup;
        Customer cust = bg.Items[0] as Customer;
        
        if (cust == null)
        {
            return new ValidationResult(false, "Customer is not the source object");
        }

        Region region = (Region)bg.GetValue(cust, "Location");
        ServiceRep rep = bg.GetValue(cust, "ServiceRepresentative") as ServiceRep;
        string customerName = bg.GetValue(cust, "Name") as string;

        if (region == rep.Area)
        {
            return ValidationResult.ValidResult;
        }
        else
        {

            StringBuilder sb = new StringBuilder();
            sb.AppendFormat("{0} must be assigned a sales representative that serves the {1} region. \n ", customerName, region);
            return new ValidationResult(false, sb.ToString());
        }
    }
}

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

注解

在方法中使用 ValidationRule.Validate 此方法可获取要提交到源的值。 返回值的类型取决于发生的阶段 ValidationRule 。 例如，如果一个TextBox数据绑定到类型为整数的属性，并且ValidationRule该调用GetValue(Object, String)已设置为RawProposedValue该ValidationStep属性，该方法将返回一个字符串。 ValidationRule如果设置了该方法ValidationStepConvertedProposedValue，该方法将返回绑定转换器返回的任何类型。 在此示例中， GetValue(Object, String) 通常返回整数。