从模板在 C# 中自动生成的代码

Question

I am now maintaining someone else's code in C# and I have found something that I am not sure I understand.

So far when I program Winforms I usually write my classes (and other code). However in this program there are some modules that have partial classes and in the header there is a commentary of the form

//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated from a template.
//
//     Manual changes to this file may cause unexpected behavior in your application.
//     Manual changes to this file will be overwritten if the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------

What are this exactly and what template are they talking about?

(*) This are not the auto-generated partial classes generated when someone design graphically a form. I have seen and used those. I suppose it is something similar but not the same

Answer 1

The comments below your question point you in the right direction for the specific case at hand but it is interesting to think about what is the general best practice when working on a project with auto generated code that is hopefully marked as such by a comment.

Well such a comment is telling you that this is not actual source code, but code that has been transpiled/generated from another source . It is indeed not the best idea to modify it directly as the process generating that code (most likely as part of the build or using a tool) can discard your changes by overwriting the file. One way to think of that is that it is a bit like if this was binary generated by the compiler (a more correct term would be intermediate language). Same would apply in that case, modifying the binary would be counter productive, error prone and the changes would be discarded by the actual compilation process.

Moreover that kind of code usually follows strict conventions and is expected to work if those conventions are scrupulously respected. One thing to have in mind is that usually such auto generated code is dumb code that is better left to a tool to be generated.

From time to time I write tools to generate code automatically, this can be very useful for things like glue code (mapping to a database, serialization, etc..). Automatically generated tests etc.. One particular example that I remember having used in real production code is stubbing . We had a wpf client that was plagged with null reference exceptions. My team was spending too much time fixing them case by case but more were appearing all the time. At some point I implemented a configurable tool that would produce code that patch the data model putting default stub objects in place of null references.