Issue with Command Timed out with data adapter

When i try to fill a dataset with a adapter am setting the command timed out
to 15 seconds. but the querry is not timing out after 15 seconds. what may be
the issue?

Code i am using
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SqlConnection objConn = new SqlConnection("Connection string");
objConn.Open();
SqlCommand objComand = new SqlCommand("select * from table1", objConn);
//Query will execute for 20 miniutes
objComand.CommandTimeout = 15; //This is not working
SqlDataAdapter sqlAdapter = new SqlDataAdapter(objComand);
//create a new dataset to hold our data
DataSet ds = new DataSet();
sqlAdapter.Fill(ds);