Checking Duplicate Values within a list using SpQuery.

using System;
using System.Runtime.InteropServices;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Serialization;
using System.Security;
using System.Web.UI.WebControls;
using Microsoft.SharePoint;
using System.Collections.Specialized;
using Microsoft.SharePoint.WebControls;
using Microsoft.SharePoint.WebPartPages;
using System.Configuration;
[assembly: AllowPartiallyTrustedCallers]

namespace TestWebPart1
{
[Guid("12084c4a-5bff-43e9-b89e-40bb11f2be86")]
public class TestWebPart1 : System.Web.UI.WebControls.WebParts.WebPart
{
TextBox txtFname;
Button btnSearchDuplicateValues;
string strError = string.Empty;
public TestWebPart1()
{

}
protected override void Render(HtmlTextWriter writer)
{
writer.Write(strError);
try
{
writer.Write(""); writer.Write(""); writer.Write(""); writer.Write(""); writer.Write(""); writer.Write(""); writer.Write(""); writer.Write(""); writer.Write("

"); writer.Write("Enter Friend Name"); writer.Write("	"); txtFname.RenderControl(writer); writer.Write("
"); btnSearchDuplicateValues.RenderControl(writer); writer.Write("

");
}
catch (Exception ex)
{
strError += ex.ToString();
}
}
protected override void CreateChildControls()
{
try
{

txtFname = new TextBox();
txtFname.ID = "txtFname";
this.Controls.Add(txtFname);

btnSearchDuplicateValues = new Button();
btnSearchDuplicateValues.ID = "btnSearchDuplicateValues";
btnSearchDuplicateValues.Text = "Check Availability";
btnSearchDuplicateValues.Click += new EventHandler(btnSearchDuplicateValues_Click);
this.Controls.Add(btnSearchDuplicateValues);
}
catch (Exception ex)
{
strError += ex.ToString();
}
}

void btnSearchDuplicateValues_Click(object sender, EventArgs e)
{
try
{
SPWeb curentWeb = SPControl.GetContextWeb(Context);
SPList lst = curentWeb.Lists["Telno"];
SPQuery sQuery = new SPQuery();
sQuery.Query = "" + txtFname.Text.ToString().ToLower() + "";
SPListItemCollection myColl = lst.GetItems(sQuery);
if (myColl.Count > 0)
{
strError += "";
}
else
{
strError += "";
}
}
catch (Exception ex)
{
strError += ex.ToString();
}
}
}
}