Dim cmd1 As New SQLCommand

    Dim cmd2 As New SQLCommand

    Dim Key As Integer

    cmd1.C \'设置数据源名称

    cmd2.C

    cmd1.commandText = "Select Count(*) F rom [单据编号] Where 单据前缀 = \'KHGL-\'"

messagebox.show("1")

    If cmd1.ExecuteScalar = 0 Then \'如果编号表不存在前缀的行,那么增加一行

        cmd1.commandtext = "In sert Into 单据编号 (单据前缀,顺序号) Values(\'KHGL-\',1)"

        cmd1.ExecuteNonQuery

    End If

    cmd1.commandText = "Select [顺序号] F rom [单据编号] Where 单据前缀 = \'KHGL-\'"

    Key = cmd1.ExecuteScalar() \'从后台获得顺序号

    cmd2.co mmandText = "Up date [单据编号] Set [顺序号] = " & (Key + 1) & " Where [顺序号] = " & Key & " And [单据前缀] = \'KHGL-\'"  

    If cmd2.ExecuteNonQuery() = 0 Then

datacolchanged事件代码看看。

另外这种编号处理建议加上事务，或者把这几条sql放到存储过程中统一调用，同样加上事务

If e.Form.Controls("TextBox2").value = "" Then

    messagebox.show("客户编号不能为空","提示!")

    e.Form.Controls("textbox3").Select()

    Return

End If

If e.Form.Controls("增 加").Enabled = True Then

    Dim dr As DataRow

    If dr.RowState <> DataRowState.Added Then \'如果不是新增行

        Return \'那么返回

    End If

    Dim cmd1 As New SQLCommand

    Dim cmd2 As New SQLCommand

    Dim Key As Integer

    cmd1.C \'设置数据源名称

    cmd2.C

    cmd1.commandText = "Select Count(*) F rom [单据编号] Where 单据前缀 = \'KHGL-\'"

    If cmd1.ExecuteScalar = 0 Then \'如果编号表不存在前缀的行,那么增加一行

        cmd1.commandtext = "Ins ert Into 单据编号 (单据前缀,顺序号) Values(\'KHGL-\',1)"

        cmd1.ExecuteNonQuery

    End If

    cmd1.commandText = "Select [顺序号] F rom [单据编号] Where 单据前缀 = \'KHGL-\'"

    Key = cmd1.ExecuteScalar() \'从后台获得顺序号

    cmd2.commandText = "Up date [单据编号] Set [顺序号] = " & (Key + 1) & " Where [顺序号] = " & Key & " And [单据前缀] = \'KHGL-\'"  

    If cmd2.ExecuteNonQuery() = 0 Then

        MessageBox.Show("客户编号重复!请重新输入!","提示")

        e.Form.Controls("textbox3").Select()

        Return 

    Else

        Dim r As Row = Tables("客户管理").addnew()

  r("客户管理系统编号") = "KHGL-" & Format(Key,"00000")

              r("单据前缀")= e.Form.Controls("TextBox8").value

        r("客户编号")= e.Form.Controls("TextBox2").value

        r("客户名称")= e.Form.Controls("TextBox3").value

        r("内部编号")= e.Form.Controls("TextBox4").value

        r("联系人")= e.Form.Controls("TextBox5").value

        r("联系电话")= e.Form.Controls("TextBox6").value

        r("联系手机")= e.Form.Controls("TextBox7").value

        r("联系地址")= e.Form.Controls("TextBox12").value

        r("备注一")= e.Form.Controls("TextBox13").value

        r("客户类别")= e.Form.Controls("ComboBox1").value

        r("货运名称")= e.Form.Controls("ComboBox2").value

        r("结算方式")= e.Form.Controls("ComboBox3").value

        r("客户区域")= e.Form.Controls("ComboBox4").value

        Tables("客户管理").current.save()

        e.Form.Controls("TextBox2").value = ""

        e.Form.Controls("TextBox3").value = ""

        e.Form.Controls("TextBox4").value = ""

        e.Form.Controls("TextBox5").value = ""

        e.Form.Controls("TextBox6").value = ""

        e.Form.Controls("TextBox7").value = ""

        e.Form.Controls("TextBox8").value = ""

        e.Form.Controls("TextBox12").value = ""

        e.Form.Controls("TextBox13").value = ""

        e.Form.Controls("ComboBox1").value = ""

        e.Form.Controls("ComboBox2").value = ""

        e.Form.Controls("ComboBox3").value = ""

        e.Form.Controls("ComboBox4").value = ""

    End If

End If

这是完整的代码呀，就是提示 未将对象引用设置到对象的实例呀，我是用做保存按钮click ，事件呀