这段代码正在使用C＃代码，但我无法在VB.net上运行。 [英] This code is working on C# code but I can't run on VB.net.

问题描述

这是错误：

无法将'System.Web.UI.WebControls.TemplateField'类型的对象强制转换为输入'System.Web.UI.WebControls.BoundField'.System Error。

 受保护的  Sub  GriView1_RowCreated（ ByVal  sender  As  对象， ByVal  e 作为 GridViewRowEventArgs）句柄 GridView1.RowCreated 
 对于 每个单元格作为 TableCell 在 e.Row.Cells 
 如果 不 字符串 .IsNullOrEmpty（ cell.Text） AndAlso （cell.Text<>  ）然后 
  Dim 字段 As  BoundField =  CType （< span class =code-keyword> CType （cell，DataControlFieldCell）.ContainingField，BoundField）
  If （field.DataField =  名称）然后 
字段。 ReadOnly  =  True  
 结束 如果 
 结束 如果 
 下一步 
 结束  Sub < /跨度> 

<二v class =h2_lin>解决方案

请参阅我对该问题的评论。如果正常工作，它就不可能是这个代码。您始终可以在C＃和VB.NET之间自动转换。请参阅我以前的回答：代码解释，C＃到VB .NET [ ^ ]。

-SA

错误信息非常清楚 - 你的网格中有一个< asp：TemplateField> ，它不是< asp：BoundField> ，所以你试图这样做会失败。



等效代码也在C＃中失败。



要使它在C＃中运行，你可以使用 为运算符 [ ^ ]并测试 null 。在VB.NET中， TryCast 运算符 [ ^ ]执行类似的功能：

 受保护的  Sub  GriView1_RowCreated（  ByVal 发​​件人作为 对象， ByVal  e  As  GridViewRowEventArgs）句柄 GridView1.RowCreated 
 对于 每个单元格作为 TableCell < span class =code-keyword>在 e.Row.Cells 
 ' 不需要比较空字符串;  
 ' 这已经由IsNullOrEmpty调用处理。 
 如果 不 字符串 .IsNullOrEmpty（cell.Text）然后 
  Dim  fieldCell  As  DataControlFieldCell =  TryCast （cell，DataControlFieldCell）
 如果 fieldCell < span class =code-keyword> IsNot   Nothing  然后 
  Dim 字段 As  BoundField =  TryCast （fieldCell.ContainingField ，BoundField）
 如果字段 IsNot   Nothing   AndAlso  field.DataField =  名称 然后 
字段。< span class =code-keyword> ReadOnly  =  True  
 结束 < span class =code-keyword>如果 
 结束 如果 
 结束 如果 
 下一步 
 结束  Sub  

This is the error:

Unable to cast object of type 'System.Web.UI.WebControls.TemplateField' to type 'System.Web.UI.WebControls.BoundField'.System Error.

Protected Sub GriView1_RowCreated(ByVal sender As Object, ByVal e As GridViewRowEventArgs) Handles GridView1.RowCreated
        For Each cell As TableCell In e.Row.Cells
            If Not String.IsNullOrEmpty(cell.Text) AndAlso (cell.Text <> "") Then
                Dim field As BoundField = CType(CType(cell, DataControlFieldCell).ContainingField, BoundField)
                If (field.DataField = "Name") Then
                    field.ReadOnly = True
                End If
            End If
        Next
    End Sub

解决方案

Please see my comment to the question. It could not be "this code" it if was "working". You can always automatically translate between C# and VB.NET. Please see my past answer: Code Interpretation, C# to VB.NET[^].

—SA

The error message is quite clear - you have a <asp:TemplateField> in your grid, which is not a <asp:BoundField>, so your attempt to cast it as such will fail.

The equivalent code would also fail in C#.

To make it work in C#, you would use the as operator[^] and test for null. In VB.NET, the TryCast operator[^] performs a similar function:

Protected Sub GriView1_RowCreated(ByVal sender As Object, ByVal e As GridViewRowEventArgs) Handles GridView1.RowCreated
    For Each cell As TableCell In e.Row.Cells
        ' No need to compare to an empty string as well; 
        ' this has already been taken care of by the "IsNullOrEmpty" call.
        If Not String.IsNullOrEmpty(cell.Text) Then 
            Dim fieldCell As DataControlFieldCell = TryCast(cell, DataControlFieldCell)
            If fieldCell IsNot Nothing Then
                Dim field As BoundField = TryCast(fieldCell.ContainingField, BoundField)
                If field IsNot Nothing AndAlso field.DataField = "Name" Then
                    field.ReadOnly = True
                End If
            End If
        End If
    Next
End Sub

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