Bug on my connection

Hi!

I have a serious problem; when I run my page its works but after inserting name on my "textbox" and click on my "button" there is a bug on this code: con.Open();

The error message is:

"login failed for user, the user is not associated with a trusted Sql server connection";

My codes:

using System;

using System.Data;

using System.Configuration;

using System.Data.SqlClient;

public partial class _Default : System.Web.UI.Page

{

public SqlConnection con;

public string constr;

public void connection()

{

constr=ConfigurationManager.ConnectionStrings["master"].ToString();

con = new SqlConnection(constr);

con.Open();

}

protected void Page_Load(object sender, EventArgs e)

{

//Label1.Visible = false;

}

private void rep_bind()

{

connection();

string query = "select * from company where Name like'" + TextBox1.Text + "%'";

SqlDataAdapter da = new SqlDataAdapter(query, con);

DataSet ds = new DataSet();

da.Fill(ds);

GridView1.DataSource = ds;

GridView1.DataBind();

}

protected void Button1_Click(object sender, EventArgs e)

{

connection();

string query = "select Name from company where Name like'" + TextBox1.Text + "%'";

SqlCommand com = new SqlCommand(query, con);

SqlDataReader dr;

dr = com.ExecuteReader();

if (dr.HasRows)

{

dr.Read();

rep_bind();

GridView1.Visible = true;

TextBox1.Text = "";

Label1.Text = "";

}

else

{

GridView1.Visible = false;

Label1.Visible = true;

Label1.Text = "The search Term " + TextBox1.Text + "  Is Not Available in the Records";

}

}