Question

我收到以下错误

无法将'System.String'类型的对象强制转换为'System.Data.DataTable'。

这是我正在使用的代码

Dim str As String = String.Empty

    If (Session("Brief") IsNot Nothing) Then

        Dim dt As DataTable = Session("Brief")
        If (dt.Rows.Count > 0) Then
            For Each dr As DataRow In dt.Rows
                If (str.Length > 0) Then str += ","
                str += dr("talentID").ToString()
            Next
        End If

    End If

    Return str

由于

Answer 1

我不是VB人，但我认为你需要将会话变量强制转换为正确的类型（DataTable）：

Dim dt As DataTable = CType(Session("Brief"), DataTable);

Answer 2

我认为你需要“演员”会议（“简报”）：

Dim dt As DataTable = CType(Session("Brief"), Datatable)

参见示例here

Answer 3

这个怎么样：

Dim str As String = ""

If Not Session("Brief") Is Nothing Then
  Dim dt As DataTable = TryCast(Session("Brief"), DataTable)

  If Not dt Is Nothing AndAlso dt.Rows.Count > 0 Then
    For Each dr As DataRow In dt.Rows
      If (str.Length > 0) Then
        str += ","
      End If

      str += dr("talentID").ToString()
    Next
  End If
End If

Return str

使用TryCast并检查演员表是否成功......

这里有一些LINQ版本可以用来衡量：

Dim str As String = ""

If Not Session("Brief") Is Nothing Then
  Dim dt As DataTable = TryCast(Session("Brief"), DataTable)

  If Not dt Is Nothing AndAlso dt.Rows.Count > 0 Then
    str = Join((From r In dt Select CStr(r("talentID"))).ToArray, ",")
  End If
End If

Return str

ASP.Net错误 - 无法将“System.String”类型的对象强制转换为“System.Data.DataTable”类型

3 个答案: