JS弹出对话框返回值代码(asp.net后台)

<script type="text/javascript"> 
function GetUser(TxtEmpID,TxtEmpName,url) 
{ 
var properties = 'status:no;resizable:no;toolbar=no;menubar=no;location=no;scroll:no;dialogWidth:540px;dialogHeight:450px;' 
var arg=window.showModalDialog(url,"",properties); 
if(arg!=null) 
{ 
document.getElementById(TxtEmpID).value=arg[0]; 
document.getElementById(TxtEmpName).value=arg[1]; 
} 
} 
</script> 
<table width="240px" cellpadding="0" cellspacing="0"> 
<tr> 
<td style="width: 80px"> 
<asp:Label ID="Label1" runat="server" Text="選擇課級別一" Width="80px" class="font-w"></asp:Label></td> 
<td style="width: 80px"> 
<asp:TextBox ID="TextBox1" runat="server" ReadOnly="false" Width="80px" onfocus="this.blur()"></asp:TextBox> 
</td> 
<td style="width: 80px"> 
<asp:TextBox ID="TextBox2" runat="server" ReadOnly="false" Width="80px" ></asp:TextBox> 
</td> 
<td style="width: 80px"> 
<asp:Button ID="Button1" runat="server" Text="確定" OnClick="Button1_Click" CssClass="ButtonCss"/> 
</td> 
<td> 
<asp:Label ID="Label3" runat="server" Text=""></asp:Label></td> 
<td> <asp:Label ID="Label4" runat="server" Text=""></asp:Label></td> 
</tr> 
</table>

protected void Page_Load(object sender, EventArgs e) 
{ 
TextBox1.Attributes.Add("onclick", "GetUser('" + this.TextBox1.ClientID + "','" + this.TextBox2.ClientID + "','WebDialog.aspx)"); 
}

<script language="javascript" type="text/javascript"> 
function Submit() 
{ 
var arr=new Array(); 
arr[0]= document.getElementById('TxtEmpID').value 
arr[1]= document.getElementById('TxtEmpCName').value 
arr[2]= document.getElementById('TxtTitleID').value 

window.returnValue=arr; 
window.close(); 
} 

</script> 
<table> 
<tr><td> 
<asp:TextBox ID="TxtEmpID" runat="server" Width="50px" ReadOnly="true" CssClass="InputCss"></asp:TextBox> 
<asp:TextBox ID="TxtEmpCName" runat="server" Width="60px" ReadOnly="true" CssClass="InputCss"></asp:TextBox> 
<asp:TextBox ID="TxtTitleID" runat="server" Width="40px" ReadOnly="true" CssClass="InputCss"></asp:TextBox> 
</tr></td> 
<tr><td> 
<input id="Button1" type="button" value="確 定" onclick="Submit()"/> 
</tr></td> 
</table>