The Result Pattern in .NET

Start by defining the Error and Result models

// Error.cs
public record Error(string Code, string Message);

// Result.cs
public class Result<T> : Result
{
   [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
   public T Value { get; }
   
   [JsonConstructor]
   private Result(bool isSuccess, T value, Error error) : base(isSuccess, error)
   {
       Value = value;
   }
   
   public static Result<T> Success(T value) => new(true, value, null!);
   public static Result<T> Failure(Error error, bool isSuccess = false) =>
       new(isSuccess, default!, error);
}

public class Result
{
   public bool IsSuccess { get; }
   public bool IsFailure => !IsSuccess;
   
   [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
   public Error Error { get; }
   
   [JsonConstructor]
   protected Result(bool isSuccess, Error error)
   {
       IsSuccess = isSuccess;
       Error = error;
   }
   
   public static Result Success() => new(true, null!);
   public static Result Failure(Error error) => new(false, error);
}

Note that the generic result type Result<T> is only required if you want to return data

Define static Error classes based on your application needs. For example:

public static class UserErrors
{
   public static Error NotFound =>
       new("NotFound", "The requested user was not found.");
    public static Error ProfileUpdateFailed =>
       new("ProfileUpdateFailed", "Failed to update user profile. Please try again later.");
}

Then use your newly found superpowers like so

if (user is null)
{
       logger.LogWarning("User not found for changing password: {UserId}", userId);
       return Result.Failure(UserErrors.NotFound);
}
// ...
logger.LogInformation("Password changed successfully for user ID: {UserId}", userId);
return Result.Success();

If you would like to return additional data, then…

return Result<UserProfileDto>.Success(user);

I'd take this over exceptions for flow-control any day. Exceptions have their place; this is not it.