What is a good rule for when to prepend members with 'this' (C#)?

Question

If I am accessing a member field, property, or method, I'm never sure when I should prepend it with 'this'.

I am not asking about cases where it is required, like in the case where a local variable has the same name. I am talking about cases where the meaning is exactly the same. Which is more readable? Are there any standards, best practices, or rules of thumb I should be following? Should it just be consistent throughout a class, or an entire code base?

Answer 1

In my code, I only use this.<PropertyName> when the property is a member of a base class, not the class I'm currently in.

Of course, not using 'this' at all is another popular choice, since it's unnecessary code being added.

Answer 2

I disagree with StyleCop on this one, and I'm not even sure that StyleCop's opinion should be interpreted as an official Microsoft guideline anyway. It was an internal tool used at Microsoft but not all teams use it, and not all teams use all the rules.

Adding this everywhere is not necessary and often just adds clutter. It does not improve performance and I'm not convinced that adding this all over the code improves readability either.

You might hear arguments that it makes it more clear where the variable is defined, but I would argue that if your class/method is so long and complicated that it is difficult to work out where something is declared then you probably should refactor it anyway. If you use the single responsibility rule and have short functions it should be obvious whether a variable is a member, a function parameter or a local variable.

As you point out, sometimes it is necessary. For example in the constructor if you want to set a private member with the same name as the parameter.

public class Foo
{
    private Bar bar;

    public Foo(Bar bar)
    {
        this.bar = bar;
    }
}

Answer 3

I recommend using Microsoft's guidelines, as verified by StyleCop: http://blogs.msdn.com/sourceanalysis/

The general rule is, prepend members with "this." when they are defined in the class, unless they are static, in which case you cannot.

Here is the rule directly from StyleCop:

SA1101: The call to {method or property name} must begin with the
'this.' prefix to indicate that the item is a member of the class.

Answer 4

If you follow Microsoft's StyleCop, you should always use prefix class members with the this keyword.

SA1101: PrefixLocalCallsWithThis
TypeName: PrefixLocalCallsWithThis
CheckId: SA1101 Category: Readability Rules

Here's a similar StackOverflow question on the same topic.

Answer 5

I usually access parameters on the current object with this. Given a naming convention for instance variables "m_", this makes it easy to see at a glance what is affected by following statements without knowing their context:

m_Height += 10;    // an instance variable
height += 10;      // a local variable
this.Height += 10; // a property

Answer 6

I would say avoid as much as possible, it saves you some(in fact a lot of) typing.

I would depend on Visual Studio more to help me to find where what belongs(never forget F12). I don't use notepad to read my cs files :P

Answer 7

Our coding standards at work state that member variables shouldn't be prefixed with 'm' or'_' or whatever else most people use. I've actually found myself using this.memberVariable all the time. I prefer the clarity over a little extra typing. And as mentioned in other answers, it's necessary when referencing parameters with the same name as member variables.

Answer 8

If you're using Visual Studio and Intellisense. When you type this you get a list of just your class level variables methods etc. Leaving out all the other possible items.