how to filter a alphanumeric value using ajax autocompleteEx

my code is...............

at .cs

[System.Web.Script.Services.ScriptMethod()]
[System.Web.Services.WebMethod]
public static List GetProduct(string prefixText)
{
OleDbConnection con = new OleDbConnection(ConfigurationManager.ConnectionStrings["LensShop"].ConnectionString);
con.Open();
OleDbCommand cmd = new OleDbCommand("select * from SKUgen where SKU_Name like @Name+'%'", con);
cmd.Parameters.AddWithValue("@Name", prefixText);
OleDbDataAdapter da = new OleDbDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
List SKU_Name = new List();
for (int i = 0; i < dt.Rows.Count; i++)
{
SKU_Name.Add(dt.Rows[i][1].ToString());
}
return SKU_Name;
}

at .aspx

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %>

> *

string value::Cri-Pol -2.25/-0.50 Ax 80 Ad -0.65

this code is working fine. but it going to stop with space character
when i typed "Cri-pol" it return values but after typing "space" Key or any numeric values, all values going to disapeare .....