elsa-workflows/elsa-core · error · InvalidOperationException

No Invoke methods were found. Use either Invoke or…

Error message

No Invoke methods were found. Use either Invoke or InvokeAsync

What it means

GetInvokeMethod throws InvalidOperationException when a middleware type exposes no public instance method named Invoke or InvokeAsync. Elsa pipelines rely on the ASP.NET Core middleware convention for invocation, so a type without such a method cannot be used as middleware. Note the message lacks a trailing period (copied from ASP.NET Core's original text).

Solutions

1. Add a public instance method named Invoke or InvokeAsync returning Task or ValueTask
2. Make sure the method is public and non-static
3. Verify the class is actually middleware-shaped rather than a handler/delegate
4. If it's a terminal handler, use the appropriate registration API instead of middleware registration

Example fix

// before
public class MyMiddleware { public Task HandleAsync(Context ctx) => Next(ctx); }
// after
public class MyMiddleware { public Task InvokeAsync(Context ctx) => Next(ctx); }

var ok = typeof(TMiddleware).GetMethods(BindingFlags.Instance | BindingFlags.Public).Any(m => m.Name is "Invoke" or "InvokeAsync"); if (!ok) throw new InvalidOperationException("Middleware lacks Invoke/InvokeAsync.");

try { pipelines.UseMiddleware<TMiddleware>(); } catch (InvalidOperationException ex) when (ex.Message.Contains("No Invoke methods")) { /* register differently or fix class */ }

When it happens

Trigger: Registering a plain class (no Invoke/InvokeAsync instance method) as middleware; defining Invoke as static, internal, or with a typo like invokeAsync; using a middleware defined only as a Func delegate type in the wrong registration overload.

Common situations: Renaming Invoke to Handle during refactoring; middleware written as an abstract base expecting a differently-named override; copy-pasting a delegate-based middleware registration for a class-based middleware.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• Multiple Invoke methods were found. Use either Invoke or…
• No Invoke methods were found. Use either Invoke or…
• Multiple Invoke methods were found. Use either Invoke or…
• The method must return Task or ValueTask
• The method must return Task or ValueTask

AI-assisted analysis of elsa-workflows/elsa-core@fe9217bdfa (2026-09-13). Data as JSON: /api/errors/4c9da8edada50a32. Report an issue: GitHub.

Appendix: source

Thrown at src/modules/Elsa.Workflows.Core/Pipelines/MiddlewareHelpers.cs:19

using System.Reflection;

namespace Elsa.Workflows.Pipelines;

public static class MiddlewareHelpers
{
    public static MethodInfo GetInvokeMethod(Type middleware)
    {
        const string invokeMethodName = "Invoke";
        const string invokeAsyncMethodName = "InvokeAsync";
        var methods = middleware.GetMethods(BindingFlags.Instance | BindingFlags.Public);
        var invokeMethods = methods.Where(m => string.Equals(m.Name, invokeMethodName, StringComparison.Ordinal) || string.Equals(m.Name, invokeAsyncMethodName, StringComparison.Ordinal)).ToArray();

        switch (invokeMethods.Length)
        {
            case > 1:
                throw new InvalidOperationException("Multiple Invoke methods were found. Use either Invoke or InvokeAsync.");
            case 0:
                throw new InvalidOperationException("No Invoke methods were found. Use either Invoke or InvokeAsync");
        }

        var methodInfo = invokeMethods[0];

        if (!typeof(Task).IsAssignableFrom(methodInfo.ReturnType) && !typeof(ValueTask).IsAssignableFrom(methodInfo.ReturnType))
            throw new InvalidOperationException($"The {methodInfo.Name} method must return Task or ValueTask");

        return methodInfo;
    }
}

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