Issue with add functionality

Question

I have an issue with add functionality
Issue is if i know the customer numbers for ex-408567346  etc ;I can write it in textboxes and by clicking on add button it has to add the customernumbers but its not working

beside add button I have serach button where we can search customernumbers and click on return it will add.
Basically two ways to add

1.Add button  ---not working
2.Search button--is working
Here is the code below

 

private void btnAddCustNum_Click(object sender, System.EventArgs e)
{
ArrayList soldTos = new ArrayList(5);
   if (txtCustNum1.Text != "") soldTos.Add(txtCustNum1.Text);
   if (txtCustNum2.Text != "") soldTos.Add(txtCustNum2.Text);
   if (txtCustNum3.Text != "") soldTos.Add(txtCustNum3.Text);
   if (txtCustNum4.Text != "") soldTos.Add(txtCustNum4.Text);
   ArrayList companies = proxy.GetCustomerList(soldTos,"");
   if (Session["USERSOLDTO"] == null)
   {
    Session["USERSOLDTO"] = companies;
    dgCustomers.DataSource = companies;
    dgCustomers.DataBind();
   }
   else
  {
    AddToCustomerGrid(companies);
    
   }
   
   Session["UPDATESOLDTOS"] = "true";
  }

 

 

Any help that could be appreciated