GenericServices.StatusGeneric

This NuGet library provides a way to return the status of a method/class that you run. It contains two main things

1. A IReadOnlyList of Errors, which may be empty. If the list is empty, then the IsValid property of the status will be true.
2. A Message which can be set by you (default value is "Success"), but if it has any errors the Message returns "Failed with nn errors".
3. The IStatusGeneric<T> version will return a Result which you can set, but returns default(T) if there are errors.

There are various methods to add errors to the Errors list, and a way to combine statuses which I show next.

NOTE: There is a companion library called EfCore.GenericServices.AspNetCore which can convert a GenericService into Model errors for ASP.NET Core MVC controllers or Razor pages, AND ASP.NET Core Web API - well worth looking at.

Simple usage examples

1. Returns just a status telling you if the method was successful. You can also set the Message in the status - default is "Success".

public IStatusGeneric NonStatusGenericString(string s)
{
    var status = new StatusGenericHandler();

    //add error and return immediately
    if (s == null)
        //You can return just an error message, but adding the property name
        //will improve the error feedback in ASP.NET Core etc.
        return status.AddError("input must not be null", nameof(s));

    status.Message = "All went well";

    //If no errors were added then its returns a IsValid status with the message
    //If there are errors then the Message says something like "Failed with 1 error"
    //and the HasErrors will be true, IsValid will be false
    return status;
}

2. Returns a status with a value

public IStatusGeneric<string> StatusGenericNumReturnString(int i)
{
    var status = new StatusGenericHandler<string>();

    //add error and return immediately
    if (i <= 0)
        return status.AddError("input must be positive", nameof(i));

    //This sets the Result property in the generic status
    status.SetResult(i.ToString());

    //If there are errors then the Result is set to the default value for generic type
    return status;
}

Typical patterns

You can use StatusGeneric in a few ways, but here is an example of the patterns I often find myself using.

public IStatusGeneric<int> StatusGenericNum(int i)
{```
    var status = new StatusGenericHandler<int>();

    //series of tests and then return all the errors together
    //Good because the user gets all the errors at once
    if (i == 20)
        status.AddError("input must not be 20", nameof(i));
    if (i == 30)
        status.AddError("input must not be 30", nameof(i));
    if (i == 40)
        status.AddError("input must not be 40", nameof(i));
    if (i == 50)
        status.AddError("input must not be 50", nameof(i));
    if (!status.IsValid)
        return status;

    //add error and return immediately
    if (i <= 0)
        return status.AddError("input must be positive", nameof(i));

    //combine error from another non-StatusGeneric method and return if has errors
    status.CombineStatuses(NonStatusGenericString(i == 10 ? null : "good"));
    if (status.HasErrors)
        return status;

    //combine errors from another generic status, keeping the status to extract later
    var stringStatus = StatusGenericNumReturnString(i);
    if (status.CombineStatuses(stringStatus).HasErrors)
        return status;

    //Do something with the Result from the StatusGenericNumReturnString method
    var combinedNums = int.Parse(stringStatus.Result) + i;
    //Set the result to be returned from this method if there are no errors
    status.SetResult(combinedNums);

    //You can put tests just before a result would be returned  - any error will set the result to default value
    if (combinedNums <= 0)
        status.AddError("input must be positive", nameof(i));

    //If you return a IStatusGeneric<T> and there are errors then
    //1. the result will be set to default value for that type
    //2  The Message will be set to "Failed with xx errors"
    return status;
}

When unit testing...

If you are testing a service its always good to check that the service returns the status you expect. If you expect it to pass then you can use this following xUnit fluent test which will

1. Test that it was a successful result
2. Show you the errors in the unit test window

status.IsValid.ShouldBeTrue(status.GetAllErrors());