private void ImageButton_qd_Click(object sender, System.Web.UI.ImageClickEventArgs e)
        {
            string str=this.DropDownList1.SelectedValue;
            if(str=="0")
            {
                this.MessageBox("请选择专业");
                return;
            }

            string script1="<script language=\"javascript\">\n"+
                "<!--\n"+
                "var array_1=new Array();\n"+
                "array_1[0]=\""+str+"\";\n"+                    
                    
                "window.returnValue=array_1;\n"+
                "window.parent.close();\n"+
                "//-->\n"+
                "</script>";
            this.RegisterClientScriptBlock("ImageButton_New_Click",script1);
        }

a页面的选择按钮的事件方法如下：

        private void Btn_Select_Click(object sender, System.EventArgs e)
        {
            string xxzt=this.TextBox1.Text.Trim();
            if(xxzt=="1")
            {
                this.Response.Redirect("O_EditItem.aspx");
            }
            if(xxzt=="2")
            {
                this.Response.Redirect("O_ItemEditHard.aspx");
            }
        }

在web视图html源文件里面需要添加js

        <script language="javascript" event="onclick" for="Btn_Select"><!--此处的for指定的是html里面选择按钮控件的ID-->
            function showwindow()
            {
                var retvalue=window.showModalDialog("b.aspx","","dialogWidth: 300px; dialogHeight: 200px");
                var array_1=new Array();
                array_1=retvalue;
                
                document.all.TextBox1.value=array_1[0];
            }
            showwindow();
        </script>