gridview wont appear

Question

i am trying to incorporate a basic search function on my webpage and display the results using a gridview. the thing, the codework on page_load but doesn't when I use a textbox + searchbutton.

heres the code:

  SqlConnection conRead = new SqlConnection
                 (@"Data Source=.\SQLEXPRESS;AttachDbFileName=|DataDirectory|\projectDB.mdf;Integrated Security=True;User Instance=True");
        SqlCommand cmdSel = new SqlCommand("SELECT * FROM Message WHERE Message LIKE '" + txtSearch.Text + "'", conRead);

        conRead.Open();

        SqlDataReader reader = cmdSel.ExecuteReader();
        GridView1.DataSource = reader;
        GridView1.DataBind();

like what i've said, it works if i put it on page_load (using select * from message) but doesn't on button1_click (using the sql statement above) where the condition parameter is based on the textbox input.

any help?