DataTable Is Always Returns Empty Values?

I'm .NET newbie and I have to write function which executes stored procedure and return DataTable.

my SqlConnection is already initialized and while running in debugger I can see DataAdapter returns values, but my DataTable is empty.

public DataTable ExecStoredProcedure(String spName, String uId)
{
DataTable dt = new DataTable();
try
{
conn.Open();
SqlCommand cmd = new SqlCommand(spName, conn);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("@UnitIDList", uId);
SqlDataAdapter da = new SqlDataAdapter(cmd);
da.Fill(dt);
}
catch (SqlException ex)
{
throw new Exception(ex.StackTrace + ex.Message);.......