C＃如何实现执行多次检查的Save方法？

Question

Often I have to deal with a save method which has to check a few things before saving to the database.

Things I check for, for example, are empty properties, and values which depends on other properties.

I am always struggling on how to implement such a things. The questions I ask myself are:

• Should I use a boolean as a return value for the Save method? And in the client code, check of it is false, show the end-user a messagebox with: "Saving failed". But the problem is, I can't show the user why saving is failed. So I don't like this one very much.
• In my Save methods, should I throw an Exception? So when a check fails, a Exception is thrown?
• Do nothing. When a check fails, just don't do anything. But I think this is not really a option.

I was wondering, how do you implement this? Is there kind of a pattern?

Answer 1

imho it's not up to the save method to validate the object. It should be valid when Save is called. It's therefore OK to throw an exception if the object is not specified correctly.

As for validation, there are built in framework in .NET which is called DataAnnotations. Use it for easier validations in all layers.

Answer 2

You should not return strings but should throw exceptions. You can create specific exceptions like EmptyPropertyException, DateOutOfBoundException etc. and throw them. Now it is up to the client to catch these exceptions to show the right error messages. Using exceptions is better as you may want to show slightly different error messages in different places or may need to use localized strings.

Answer 3

Very nice implementation is offered by Enterprise Library - Validation block. Please see level of details and ease of implementation on following location:

http://msdn.microsoft.com/en-us/library/ff953192%28v=PandP.50%29.aspx

Answer 4

It dependes on what you need and on what user needs...
Basicly you could return a string: if is null or empty everything is ok, on the contrary this string is the error. So you can show a MessageBox or take whatever action you please.
Usually I prefer doing nothing server-side (if there is an error) and returning the error itself, so client-side I can take actions or let user decide what to do.
You can even return an exception from server if there is an error or null if everything went ok.

Answer 5

如果您想知道保存失败的原因，请使用它们所针对的异常。

Answer 6

我将使用类似结果状态的结果-具有布尔属性的对象，显示操作是否成功，如果发生某些错误并发生异常，则向用户显示一条消息。