Question

我有以下代码。

Dim hardlimit As DataTable = From f In dealDataTable.AsEnumerable
                                    Join f2 In hardlimithit.AsEnumerable
                                    On f.Field(Of Integer)("dea_ID") Equals f2.Field(Of Integer)("ID")
                                    Select f

我试图从＆＃34; dealDataTable＆＃34;中选择获取所有数据。其中id与我的其他数据表的id字段匹配。

我从此代码中收到此错误。

System.InvalidCastException was caught
  HResult=-2147467262
  Message=Unable to cast object of type '<JoinIterator>d__61`4[System.Data.DataRow,System.Data.DataRow,System.Int32,System.Data.DataRow]' to type 'System.Data.DataTable'.
  Source=FMSOvernight
  StackTrace:
       at FMSOvernight.Module1.RunLimitCalculations() in C:\Cloud Source Control\Funding Management Overnighter\FundingManagementSystemOvernightRoutine\Module1.vb:line 273
       at FMSOvernight.Module1.StartGeneration() in C:\Cloud Source Control\Funding Management Overnighter\FundingManagementSystemOvernightRoutine\Module1.vb:line 135
  InnerException:

Answer 1

您选择IEnumerable<DataRow>行，而不是DataTable。您可以使用CopyToDataTable：

Dim hardlimitRows = From f In dealDataTable.AsEnumerable
                    Join f2 In hardlimithit.AsEnumerable
                    On f.Field(Of Integer)("dea_ID") Equals f2.Field(Of Integer)("ID")
                    Select f
Dim hardlimitTable = hardlimitRows.CopyToDataTable()

但请注意，如果没有行，此方法将抛出InvalidOperationException。你必须先检查一下。例如：

Dim hardlimitTable As DataTable = dealDataTable.Clone() ' empty table with the same columns '
If hardlimitRows.Any() Then
    hardlimitTable = hardlimitRows.CopyToDataTable()
End If

在linq中连接两个数据表时出错

1 个答案: