控件操作

我们在写窗体的时候，总是会遇到很多判断控件的显示内容是否为空或者清空其显示信息，为了代码的清洁，我们最好把这些重复的内容写到一个单独的类模块里，下面我来说一下我是如何操作的（我以文本框和组合框为例做了一个Demo）：

     Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        If TestEmpty(TextBox1, Label2) Then Exit Sub
        If TestEmpty(ComboBox1, Label1) Then Exit Sub
        Clear(TextBox1)
        Clear(ComboBox1)
    End Sub

    ''' <summary>
    ''' 清空控件的显示信息
    ''' </summary>
    ''' <param name="ctrl">需要清空的控件对象</param>
    ''' <remarks>2011-4-22 19:19 by dan</remarks>
    Private Sub Clear(ByVal ctrl As Control)
        If (TypeOf ctrl Is TextBox) Then
            ctrl.Text = ""
        ElseIf (TypeOf ctrl Is ComboBox) Then
            ctrl.Text = ""
            CType(ctrl, ComboBox).SelectedIndex = -1
        End If
    End Sub

    ''' <summary>
    ''' 测试控件的显示信息是否为空
    ''' </summary>
    ''' <param name="ctrl">需要判断的控件对象</param>
    ''' <param name="ctrlshow" >判断控件的标签对象</param>
    ''' <remarks>2011-4-22 19:20 by dan</remarks>
    Private Function TestEmpty(ByVal ctrl As Control, ByVal ctrlshow As Control) As Boolean
        Dim result As Boolean

        If Trim(ctrl.Text) = "" Then
            MsgBox(ctrlshow.Text & "不能为空！", vbOKOnly + vbInformation, "提示")
            ctrl.Focus()
            result = True
        Else
            result = False
        End If
        Return result
    End Function<!--
.csharpcode, .csharpcode pre
{
	font-size: small;
	color: black;
	font-family: consolas, "Courier New", courier, monospace;
	background-color: #ffffff;
	/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt 
{
	background-color: #f4f4f4;
	width: 100%;
	margin: 0em;
}
.csharpcode .lnum { color: #606060; }
--><!--
.csharpcode, .csharpcode pre
{
	font-size: small;
	color: black;
	font-family: consolas, "Courier New", courier, monospace;
	background-color: #ffffff;
	/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt 
{
	background-color: #f4f4f4;
	width: 100%;
	margin: 0em;
}
.csharpcode .lnum { color: #606060; }
-->

注意：清空的时候，一般只有Text属性的只需调用共用控件类的Text属性清空即可，但是对于如组合框这样还需要清空列表框中的选择的信息的，则需要将控件转换其类型然后对相应的属性进行操作