date time problem

First: You are not using a parameter, it's just passed into a string.

Second: "net amount" there can be NO spaces in column names within your table.

Third: Tostring() does not exist. It has to be ToString();

How this should be done is:

(My demo uses OleDb but the practice is overall the same)

string sqlQuery = "SELECT billno, net_amount FROM bill_details WHERE date=@Date";

OleDbCommand sqlCommand = new OleDbCommand(sqlQuery, sqlConnection);
sqlCommand.Parameters.Add("@Date", OleDbType.VarChar).Value = DateTime.Now.ToString();

OleDbDataAdapter sqlAdapter = new OleDbDataAdapter(sqlCommand);

DataSet ds = new DataSet();
sqlAdapter.Fill(ds);

Now all information should be in DataSet ds. And can be bound as a DataSource to a DataGridView or be read manually progammetically.