在使用activeX“组合框”控件时必须点击两次按钮才能提交？

Question

<OBJECT id="ComboBox1" height="21" width="184" classid="clsid:8BD21D30-EC42-11CE-9E0D-00AA006002F3"
name="ComboBox1" VIEWASTEXT>
<PARAM NAME="VariousPropertyBits" VALUE="746604571">
<PARAM NAME="BackColor" VALUE="2147483653">
<PARAM NAME="ForeColor" VALUE="2147483656">
<PARAM NAME="MaxLength" VALUE="0">
<PARAM NAME="BorderStyle" VALUE="0">
<PARAM NAME="ScrollBars" VALUE="0">
<PARAM NAME="DisplayStyle" VALUE="3">
<PARAM NAME="MousePointer" VALUE="0">
<PARAM NAME="Size" VALUE="4868;556">
<PARAM NAME="PasswordChar" VALUE="0">
<PARAM NAME="ListWidth" VALUE="0">
<PARAM NAME="BoundColumn" VALUE="1">
<PARAM NAME="TextColumn" VALUE="65535">
<PARAM NAME="ColumnCount" VALUE="1">
<PARAM NAME="ListRows" VALUE="8">
<PARAM NAME="cColumnInfo" VALUE="0">
<PARAM NAME="MatchEntry" VALUE="1">
<PARAM NAME="ListStyle" VALUE="0">
<PARAM NAME="ShowDropButtonWhen" VALUE="2">
<PARAM NAME="ShowListWhen" VALUE="1">
<PARAM NAME="DropButtonStyle" VALUE="1">
<PARAM NAME="MultiSelect" VALUE="0">
<PARAM NAME="Value" VALUE="">
<PARAM NAME="Caption" VALUE="">
<PARAM NAME="PicturePosition" VALUE="458753">
<PARAM NAME="BorderColor" VALUE="2147483654">
<PARAM NAME="SpecialEffect" VALUE="2">
<PARAM NAME="Accelerator" VALUE="0">
<PARAM NAME="GroupName" VALUE="">
<PARAM NAME="FontName" VALUE="System">
<PARAM NAME="FontEffects" VALUE="1073741825">
<PARAM NAME="FontHeight" VALUE="165">
<PARAM NAME="FontOffset" VALUE="0">
<PARAM NAME="FontCharSet" VALUE="134">
<PARAM NAME="FontPitchAndFamily" VALUE="34">
<PARAM NAME="ParagraphAlign" VALUE="1">
<PARAM NAME="FontWeight" VALUE="700">
</OBJECT>
private void Button1_Click(object sender, System.EventArgs e)
{
Response.Write(Request.Form["ComboBox1"].ToString());
}
点击第一次按钮后没输出任何内容。
点击第二次后才能看到输出。请问怎么解决，谢谢！