Why Are My C# Prepared Statements with MySQL Failing, and How Can I Fix Them?

Prepared Statement Usage in C# with MySQL

In an attempt to employ prepared statements in a C# program, developers may encounter difficulties. One common issue arises when the prepared statement code is replaced with a regular statement, resulting in successful execution.

Upon close examination, it is evident that the prepared statement is not being configured correctly. Here are the key steps to properly utilize prepared statements:

1. Create a MySqlCommand object with the desired query containing parameter placeholders (e.g., @val1).
2. Add parameters to the command object using the AddWithValue method.
3. Prepare the command by calling the Prepare method. This step ensures that the database server parses and optimizes the SQL statement.

The following example demonstrates the corrected prepared statement usage:

private void btnLogin_Click(object sender, EventArgs e)
{
    MySqlCommand cmd = MySqlConn.cmd;
    cmd = new MySqlCommand("SELECT * FROM admin WHERE admin_username=@val1 AND admin_password=PASSWORD(@val2)", MySqlConn.conn);
    cmd.Parameters.AddWithValue("@val1", tboxUserName.Text);
    cmd.Parameters.AddWithValue("@val2", tboxPassword.Text);
    cmd.Prepare();
    MySqlDataReader res = cmd.ExecuteReader();
    if (!res.HasRows) { MessageBox.Show("Error! "); res.Close(); return; }
    else
    {
        //do something
    }
    res.Close();
}

In this revised code, the single quotes (') surrounding the parameter values in the query are removed. Additionally, the Prepare method is called after adding the parameters. By adhering to these steps, prepared statements can be effectively utilized in C# programs with MySQL.

The above is the detailed content of Why Are My C# Prepared Statements with MySQL Failing, and How Can I Fix Them?. For more information, please follow other related articles on the PHP Chinese website!