C# search textbox autocomplete with any letter

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C#

i have a textbox1 and it's autocomplete source is on database .. but it's not working as it should .. as an example :

I have on my table these names :

united states
united kingdom


and the user start typing "kingdom" no suggestion appear only when I type it from the beginning "united kingdom"

I need the suggestion appear if I type starting from the middle or end or beginning

What I have tried:

cm = new SqlCommand();
cm.Connection = cn;
string searchFor = "%" + textBox1.Text + "%"; //the string the user entered.
AutoCompleteStringCollection namecollection = new AutoCompleteStringCollection();
cm.CommandText = @"SELECT distinct itmname AS name FROM table1 WHERE name LIKE @name";

cm.Parameters.AddWithValue("@name", searchFor);
SqlDataReader rea = cm.ExecuteReader();
if (rea.HasRows == true)
{
    while (rea.Read())
        namecollection.Add(rea["name"].ToString());
}
rea.Close();
autoCompleteTextbox1.AutoCompleteCustomSource = namecollection;