Question

string sql = "select * from customer where name like '" + textBox2.Text + "%'";
string sql2 = "select * from customer";

if (textBox2.Text.Length > 0)
{
    DataTable dt = CarDatabase.executeSelect(sql);
    DataTable dt2 = CarDatabase.executeSelect(sql2);

    if (dt == null)
    {
        dataGridView2.DataSource = dt2;
        MessageBox.Show("There's no result with " + textBox2.Text);
    }
    else if (dt != null)
        dataGridView2.DataSource = dt;
}
else
{
    MessageBox.Show("Please fill the textbox");
}

I try to do “if like has some result, show it in DataGrid“. There’s no problem with that. However, when like finds nothing in the database, the DataGrid stays old. However, if after searching there is no result, the DataGrid is empty.

Answer 1

Well it is a good practice to use a stored procedure than injecting sql query from the code.

I would have created a procedure something like this…

Create Procedure GetCustomers(@name varchar(100))
AS 
BEGIN
 select * from customer  where Name like (ISNULL(@name,Name))
END

However while passing value to the @name parameter, you need to append ‘%’ to it. If textbox value is empty then pass null to @name. This query will return all customer if textbox value is empty else the requested customers.