I can't tell you for sure why they didn't keep them different. It's likely that nobody can unless someone who took part in creating the standards happens to see this question.

Many people create their own conventions by prefixing instance variables with _ or m_, but I really don't think it matters. You can infer a lot from context and IDEs these days are smart enough to help you out. Visual Studio with the ReSharper addon, for example, will show you local variables and instance variables in different colours.

If it really matters that you differentiate between the two scopes, you can use the this. prefix to refer to the instance variable:

public class Test
{
    private int myInteger;

    void SomeMethod(int myInteger)
    {
        this.myInteger = 10; // sets instance variable to 10
        myInteger = 10; // does not affect the instance variable.
    }
}

Without any other plugins, Visual Studio will by default help you with Intellisense:

(The pop-up may still be styled by ReSharper there, but ReSharper doesn't add anything to the features of built-in Intellisense, so while the stock one might look a little different, it'll still have both options in there.)

I can't tell you for sure why they didn't keep them different. It's likely that nobody can unless someone who took part in creating the standards happens to see this question.

Many people create their own conventions by prefixing instance variables with _ or m_, but I really don't think it matters. You can infer a lot from context and IDEs these days are smart enough to help you out. Visual Studio with the ReSharper addon, for example, will show you local variables and instance variables in different colours.

If it really matters that you differentiate between the two scopes, you can use the this. prefix to refer to the instance variable:

public class Test
{
    private int myInteger;

    void SomeMethod(int myInteger)
    {
        this.myInteger = 10; // sets instance variable to 10
        myInteger = 10; // does not affect the instance variable.
    }
}

Without any other plugins, Visual Studio will by default help you with Intellisense:

(The pop-up may still be styled by ReSharper there, but ReSharper doesn't add anything to the features of built-in Intellisense, so while the stock one might look a little different, it'll still have both options in there.)

You can also use code analysis tools like FxCop and StyleCop to help you catch potential problems with variable naming and scope.