Web Forms :: Changing Textbox To DDL?

I have a webform with difrent parts in it, its like a search criteria, noissues with other parts but theres one part in it called guest profile which is giving me problems.There was a field name called guest company with a textbox by its side, when the user enters the company name and clicks enter it displays the list of people with that company name

but now I have changed this textbox to ddl and populated this ddl with the company names now when I am selecting this company name and clicking enter its not showing the data the code for the above issue is shown below I have also posted the stored procedure used in this

the code used to design the DDL

<tr>
<th>
Guests Company:
</th>
<td>
<asp:DropDownList ID="ddlCompanyName" runat="server" CssClass="default" />
</td>
</tr>
the code used to bind the data to this ddl
protected void BindCompanyDDL()
{
var companyList = Company.FindAll();
ddlCompanyName.Items.Add(new ListItem("- Select Company -", ""));
foreach (var companyDetail in companyList)
{
ddlCompanyName.Items.Add(new ListItem(companyDetail.Name, companyDetail.Id.ToString()));
}
ddlCompanyName.DataBind();
}
the code used to initialize search
public void InitializeSearch(ref RecipientSearchParams searchParams)
{
if (!String.IsNullOrEmpty(txtGuestName.Text))
searchParams.GuestName = HttpContext.Current.Server.HtmlEncode(txtGuestName.Text);
if (ddlCompanyName.SelectedValue != String.Empty)
searchParams.CompanyName = ddlCompanyName.SelectedValue;
if (ddlCompanyType.SelectedValue != String.Empty)
searchParams.CompanyType = ddlCompanyType.SelectedValue;

the code used to load parameter values

public void LoadParamValues(RecipientSearchParams searchParams)
{
if (!String.IsNullOrEmpty(searchParams.GuestName))
txtGuestName.Text = searchParams.GuestName;
if (!String.IsNullOrEmpty(searchParams.CompanyName))
ddlCompanyName.SelectedValue = searchParams.CompanyName;
if (!String.IsNullOrEmpty(searchParams.CompanyType))
ddlCompanyType.SelectedValue = searchParams.CompanyType;
public interface IAudenceTab
{
bool ValidateSearch();
void InitializeSearch(ref RecipientSearchParams searchParams);
void LoadParamValues(RecipientSearchParams searchParams);
}
private void PopulateGuestSqlParams()
{
if (!String.IsNullOrEmpty(GuestName))
{
AddHashValue("GuestName", _GuestName);
Description += String.Format("Guest Name {0}; ", _GuestName);
}
if (!String.IsNullOrEmpty(CompanyName))
{
AddHashValue("CompanyName", CompanyName);
Description += String.Format("Company Name {0}; ", CompanyName);
}
if (!String.IsNullOrEmpty(CompanyType))
{
AddHashValue("CompanyType", CompanyType);
Description += String.Format("Company Type {0}; ", CompanyType);
}
public List<Person> ExecuteSearch()
{
PopulateSqlParams();
MSSqlDBProvider db = new MSSqlDBProvider();
SqlConnection conn = db.GetConnection();
List<Person> pList =
DataObjectProvider<Person>.GetObjectList("dbo.PersonNewsletterFilterSearch", CommandType.StoredProcedure,
pHash, conn);
return pList;
}
stored procedure used
(@GuestName IS NULL OR p.FullName LIKE '%' + @GuestName + '%') AND
(@CompanyName IS NULL OR p.ID IN (
SELECT Distinct compGuest.GuestId From CompanyGuest compGuest
Inner Join CompanyDetail compDetail on compGuest.CompanyId = compDetail.PersonId
where compDetail.[Name] = @CompanyName )) AND
(@CompanyType IS NULL OR p.ID IN (
SELECT Distinct compGuest.GuestId From CompanyGuest compGuest
Inner Join CompanyDetail compDetail on compGuest.CompanyId = compDetail.PersonId
where compDetail.[Type] = @CompanyType)) AND