Dim Name As String = e.Form.Controls("Name").Value
Dim cmd As New SQLCommand
Dim dt As DataTable
Dim dr As DataRow
cmd.C
If Name = "" Then
    Messagebox.show("请选择或输入用户登录名!","提示",MessageBoxButtons.OK,MessageBoxIcon.Information)
    Return
End If
cmd.CommandText = "Select * From {用户} Where [登录名] = \'" & Name & "\'"
dt = cmd.ExecuteReader
dr = dt.DataRows(0)
If dt.DataRows.Count = 0 Then \'返回1表示更改成功
    Messagebox.show("用户名输入错误!","提示",MessageBoxButtons.OK,MessageBoxIcon.Information)
    Return
Else
    If  dr("禁用") = True Then
        Messagebox.show("此用户已禁用,请与管理员联系!","提示",MessageBoxButtons.OK,MessageBoxIcon.Information)
        Return
    Else
        If e.Form.Controls("PassWord").Value = dr("密码") Then
            _Name = Name
            _UserName = dr("用户名")
            _UserGroup = dr("用户组")
            _UserJS = dr("角色")
            e.Form.Close
        Else
            Messagebox.show("密码错误!","提示",MessageBoxButtons.OK,MessageBoxIcon.Information)
        End If
    End If

登录时输入的用户名不在用户表中，确定时出现“超出数组范围”的错误提示

cmd.CommandText = "Select * From {用户} Where [登录名] = \'" & Name & "\'"
dt = cmd.ExecuteReader
dr = dt.DataRows(0)

改为：

cmd.CommandText = "Select * From {用户} Where [登录名] = \'" & Name & "\'"
dt = cmd.ExecuteReader
if  dt.Datarows.Count = 0 then

    Messagebox.show("用户名错误!","提示",MessageBoxButtons.OK,MessageBoxIcon.Information)

    return

End if

dr = dt.DataRows(0)