LA0226: Argument Name Not Found


Severity	Error
Reported by	PostSharp
Message	`The parameter "<Parameter>" of the advice "<Advice>" is bound by [Argument("<Name>")], but "<TargetMethod>" has no parameter named "<Name>".`

Cause

The ArgumentAttribute(string) constructor binds a parameter of an advice to the argument of the target method that has a given name. PostSharp looks for the name in each target method of the advice, with a case-sensitive comparison. When a target method has no parameter of this name, it reports LA0226 on that method.

When the advice uses a pointcut that skips the targets whose signature does not match, such as MatchPointcut, PostSharp skips the target instead of reporting the error.

In the following example, the [LogCustomer] aspect reads the customerId argument, but the CountInvoices method names its parameter id.

Full screen

using System;
using PostSharp.Aspects;
using PostSharp.Aspects.Advices;
using PostSharp.Serialization;

namespace Errors.LA0226_Error;

[PSerializable]
public sealed class LogCustomerAttribute : MethodLevelAspect
{
    [OnMethodEntryAdvice]
    public void OnEntry( [DeclarationName] string methodName, [Argument( "customerId" )] int customerId )
    {
        Console.WriteLine( $"{methodName}: customer {customerId}" );
    }
}

public class OrderService
{
    [LogCustomer]
    public int CountOrders( int customerId ) => 3;

    // The parameter is named id, not customerId.
    [LogCustomer]
    public int CountInvoices( int id ) => 2;
}

public static class Program
{
    public static void Main()
    {
        OrderService service = new();
        Console.WriteLine( service.CountOrders( 42 ) );
        Console.WriteLine( service.CountInvoices( 42 ) );
    }
}

Full screen

error LA0226: LA0226_Error.cs(25,16): The parameter "customerId" of the advice "Errors.LA0226_Error.LogCustomerAttribute.OnEntry(System.String, System.Int32)" is bound by [Argument("customerId")], but "Errors.LA0226_Error.OrderService.CountInvoices(System.Int32)" has no parameter named "customerId".

Resolution

Rename the parameter of the target method, or the name given to the ArgumentAttribute, so that they match, including the case.
Select the argument by its index or by its type when the target methods do not name it in the same way.
Otherwise, apply the aspect only to methods that have a parameter of this name.

In the following example, the parameter of CountInvoices has the name that the aspect expects.

Full screen

using System;
using PostSharp.Aspects;
using PostSharp.Aspects.Advices;
using PostSharp.Serialization;

namespace Errors.LA0226_Fixed;

[PSerializable]
public sealed class LogCustomerAttribute : MethodLevelAspect
{
    [OnMethodEntryAdvice]
    public void OnEntry( [DeclarationName] string methodName, [Argument( "customerId" )] int customerId )
    {
        Console.WriteLine( $"{methodName}: customer {customerId}" );
    }
}

public class OrderService
{
    [LogCustomer]
    public int CountOrders( int customerId ) => 3;

    // The parameter has the name that the aspect expects.
    [LogCustomer]
    public int CountInvoices( int customerId ) => 2;
}

public static class Program
{
    public static void Main()
    {
        OrderService service = new();
        Console.WriteLine( service.CountOrders( 42 ) );
        Console.WriteLine( service.CountInvoices( 42 ) );
    }
}

Full screen

CountOrders: customer 42
3
CountInvoices: customer 42
2

Cause

Resolution

See Also