How to Avoid IndexOutOfBoundsException When Using Parameterized Queries with MySQL in C#?

Parameterized Query for MySQL with C#

When working with SQL queries, parameterized queries are highly recommended. They protect against SQL injection attacks and improve performance by eliminating the need to concatenate string values.

However, when using parameterized queries with MySQL from C#, it's important to ensure that your code is configured correctly. One potential error that can occur is an IndexOutOfBoundsException when adding the first parameter.

The Issue:

In the given code:

private String readCommand = "SELECT LEVEL FROM USERS WHERE VAL_1 = ? AND VAL_@ = ?;";

The problem lies in the query string, which uses a question mark (?) as the placeholder for parameters. MySQL doesn't recognize question marks as parameter placeholders; it expects named parameters prefixed with '@'.

The Solution:

To fix the issue, you need to modify the query string to use named parameters and add the parameters to the MySqlCommand object using the AddWithValue() method:

private String readCommand = "SELECT LEVEL FROM USERS WHERE VAL_1 = @param_val_1 AND VAL_2 = @param_val_2;";

public bool read(string id)
{
    level = -1;
    MySqlCommand m = new MySqlCommand(readCommand);
    m.Parameters.AddWithValue("@param_val_1", val1);
    m.Parameters.AddWithValue("@param_val_2", val2);
    level = Convert.ToInt32(m.ExecuteScalar());
    return true;
}

By using named parameters and the AddWithValue() method, the query will be executed successfully without encountering an IndexOutOfBoundsException.

The above is the detailed content of How to Avoid IndexOutOfBoundsException When Using Parameterized Queries with MySQL in C#?. For more information, please follow other related articles on the PHP Chinese website!