How to Resolve IndexOutOfBoundsException in MySQL Parameterized Queries with C#?

Parameterized Queries in MySQL with C#: Addressing IndexOutOfBoundsException

When working with parameterized queries in MySQL using C#, it's important to ensure that the parameter names and values are correct to avoid exceptions. In this case, an IndexOutOfBoundsException is encountered while adding the first parameter.

To resolve this issue, verify that the parameter names in the query string and the parameters added to the MySqlCommand object match. Additionally, consider the following:

Mismatched Parameter Names

In the provided code:

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

You have mistakenly used ? placeholders in the query string, which are not supported by MySQL. Instead, MySQL expects named parameters, which should begin with @.

Code Changes

Replace the query string with the following:

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

Additionally, use the AddWithValue method to add parameters to the command object:

m.Parameters.AddWithValue("@param_val_1", val1);
m.Parameters.AddWithValue("@param_val_2", val2);

This ensures that the parameter names match the placeholders in the query string.

Return Value

In the modified code, the level value is retrieved using ExecuteScalar instead of ExecuteReader. This is because the query returns a single value (level), so using ExecuteScalar is more efficient.

By making these changes, you should be able to execute the parameterized query without encountering any exceptions.

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