showing aspx page as a popup

i have two pages one in index.html and one in EnquireTest.aspx 

    
     Enquire now

after clicking above popup will get open, popup code

 

     

         


             
             

                 
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and below is my aspx code

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="EnquireTest.aspx.cs" Inherits="ApplicationForm.LandingPage.EnquireTest" %>

<%@ Register Assembly="MSCaptcha" Namespace="MSCaptcha" TagPrefix="cc1" %>






    
   




    

        

            
            
                

                    

                        

                            <%----%>
                        
                    
                    

                        

                            
                            
                        


                        

                            <%----%>
                        
                    
                    

                        <%-- 

                                
                                
                            
--%>
                        

                            
                            
                            
                        

                    
                    

                        

                            <%----%>
                        
                    
                    

                        <%-- 

                                
                                
                            
--%>
                        

                            
                            
                            
                        

                    
                    

                        

                            <%----%>
                        
                    
                    

                        

                            
                                Select Locations
                            
                            
                        
                    
                    

                        

                            <%----%>
                        
                    
                    

                        

                            
                                Select Course
                            
                            
                        
                    
                    

                        

                            
                            
                        
                    
                    

                        


                            
                        
                    


                    

                        

                    
                
            
        

        

            
        
    

    
     
  
  
  

   



       

and this is my is my EnquireTest.aspx.cs

 protected void btnSubmit_Click(object sender, EventArgs e)
 {
     Captcha1.ValidateCaptcha(txtCaptcha.Text.Trim());
     if (Captcha1.UserValidated)
     {
         DataSet dss = new DataSet();
         a.Mode = "InsertEnquiry";
         a.StudentName = txtName.Text.Trim();
         a.EmailID = txtEmailID.Text.Trim();
         a.MobileNumber = txtMobileNo.Text.Trim();
         a.Location = ddlLocations.SelectedItem.Text.ToString();
         a.Course = ddlCourse.SelectedItem.Text.Trim();
         dss = objDal.getEnquiry(a);
         if (dss.Tables[0].Rows.Count > 0)
         {
             // Display success message
             txtName.Text=string.Empty;
             txtEmailID.Text = string.Empty;
             txtMobileNo.Text = string.Empty;
             ddlLocations.SelectedIndex = 0;
             ddlCourse.SelectedIndex = 0;
             txtCaptcha.Text = string.Empty;
             ClientScript.RegisterClientScriptBlock(this.GetType(), "alert", "alert('Information saved succesfully')", true);
           
         }
         else
         {
             // Display error message
             ClientScript.RegisterClientScriptBlock(this.GetType(), "alert", "alert('Error in inserting Application')", true);
         }
     }
     else
     {
         // Display captcha error message
         ClientScript.RegisterClientScriptBlock(this.GetType(), "alert", "alert('Enter Correct Captcha Code')", true);
     }
 }

after clicking on submit textbox value is not getting to empty. it is still showing entered value. and also the after clciking on submit debugger is not getting called.
Please give me solution.