BindingGroup.GetValue(Object, String) 方法

定義

命名空間:
System.Windows.Data
組件:
PresentationFramework.dll

傳回指定之屬性和項目的建議值。

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

參數

item
Object

包含指定屬性的物件。

propertyName
String

該房產的提議價值。

傳回

Object

建議的房產價值。

例外狀況

InvalidOperationException

指定物品和屬性沒有約束。

ValueUnavailableException

指定屬性的值無法取得，原因可能是轉換錯誤或先前驗證規則失敗。

範例

以下範例是一個應用程式的一部分，該應用程式會提示使用者輸入多個客戶，並為每位客戶指派一位銷售代表。 申請會檢查銷售代表與顧客是否屬於同一地區。 範例展示了 Validate 該方法，利用該 GetValue(Object, String) 方法取得客戶輸入的數值。

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

備註

在方法 ValidationRule.Validate 中使用此方法，取得將要提交給原始碼的值。 回報值的類型取決於該現象 ValidationRule 發生的階段。 例如，若 a TextBox 綁定於一個型別為整數的屬性，且ValidationRule該呼叫GetValue(Object, String)的設定ValidationStep為 RawProposedValue ，該方法回傳一個字串。 若 設定ValidationRuleValidationStep為 ConvertedProposedValue，該方法回傳綁定轉換器所回傳的類型。 在這個例子中，通常 GetValue(Object, String) 回傳一個整數。

適用於