asp.net - asp.net, ExecuteReader requires an open and available Connection

Question

I have this code on a method:

DataGrid2.DataSource = Show1(Convert.ToInt32(Request.QueryString["Cr"]));
DataGrid2.DataBind();

this is the show method that is asigned to the datasource:

static SqlConnection sqlConntest = new SqlConnection( ConfigurationSettings .AppSettings["conn"].ToString () );

public static SqlDataReader Show1(int cr)
 {
   SqlDataReader dr;
                SqlCommand cmd = new SqlCommand();
                cmd.Connection = sqlConntest;
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.CommandText = "sp1";
                cmd.Parameters.Add("@Cr", SqlDbType.Int);
                cmd.Parameters["@Cr"].Value = crewID;
 sqlConntest.Open();
                dr = cmd.ExecuteReader();

                return dr;
}

when I run the program I get the error message:

"ExecuteReader requires an open and available Connection. The connection's current state is closed"

Why is this happening and how can I solve this? thanks.