Question

我正在尝试计算已保存数据的记录这是我的代码：

    Dim pl_qry As String
    Dim pl_cmd As New Odbc.OdbcCommand
    Dim pl_dr As Odbc.OdbcDataReader

    If txtPurpose.Text = "PERSONAL LOAN" Then
        pl_qry = "select count(purpose) from details where borrower_id = '" & bor_id & "' and purpose = '" & "PERSONAL LOAN" & "'"
        pl_cmd.CommandText = pl_qry
        pl_cmd.Connection = con
        pl_dr = pl_cmd.ExecuteScalar

        pl_dr.Read()
        If Not pl_dr.IsDBNull(0) Then
            MsgBox(pl_dr.GetString(0))
        End If
    End If

我在这一行得到了错误

    pl_dr = pl_cmd.ExecuteScalar

Answer 1

如果您检查了ExecuteScalar方法，您会发现它将返回SQL第一行的第一列。

问题是您已将结果分配给'OdbcDataReader`

Dim pl_dr As Odbc.OdbcDataReader

但也许你可以直接得到结果：

Int64 result = Convert.ToInt64(cmd.ExecuteScalar())

错误：无法将类型为“System.Int64”的对象强制转换为“System.Data.Odbc.OdbcDataReader”

1 个答案: