参考帮助 做的自定义用户管理 在增加用户时候 当已有重复用户的时候会报错~

怎么解决

代码如下

Dim UserName As String = e.Form.Controls("UserName").Value
Dim UserGroup As String = e.Form.Controls("UserGroup").Value
Dim PassWord As String = e.Form.Controls("PassWord").Value
Dim Department As String = e.Form.Controls("Department").Value
Dim cmd As New SQLCommand
cmd.C
If UserName = "" OrElse  UserGroup = "" OrElse PassWord= "" Then
    Messagebox.show("请输入帐号名,密码和用户分组!","提示",MessageBoxButtons.OK,MessageBoxIcon.Information)
    Return
End If
cmd.CommandText = "Insert Into {Users} ([Name],[Group],[Password],[Department]) Values (\'"
cmd.CommandText = cmd.CommandText & UserName & "\',\'" & UserGroup & "\',\'" & Password & "\',\'" & Department & "\')"
If cmd.ExecuteNonQuery = 1 Then \'返回1表示增加成功
    Dim Result As DialogResult
    Result = MessageBox.Show("增加用户成功!是否继续增加", "提示", MessageBoxButtons.YesNo, MessageBoxIcon.Question)
    If Result = DialogResult.Yes Then
    Else
        If Forms("用户管理").Opened Then
            With Forms("用户管理").Controls("ListBox1")
                .Items.Add(UserName)
                .SelectedIndex = .Items.Count -1
            End With
        End If
        e.Form.Close()
    End If
Else
    Messagebox.show("增加用户失败, 可能存在同名用户!","提示",MessageBoxButtons.OK,MessageBoxIcon.Information)
End If

知道是这个原因 是增加了 同名用户 才出错

我要的是增加同名用户时不出错 出口个提示对话框~

不知道怎么处理