Failed to compile code due to <, > and $ symbols

Question

I have a C# code of an assembly which fails to build in visual studio. After some research I found out all these errors are caused by <, > and $ symbols. Analyzing the assembly in .NET reflector turns out these parts of the code were created by the compiler. Here is a bit of code with these errors

    private System.Collections.IEnumerator Register(string name, string password, string password2, string email)
{
    LoginFengKAI.<Register>c__Iterator2 <Register>c__Iterator = new LoginFengKAI.<Register>c__Iterator2();
    <Register>c__Iterator.name = name;
    <Register>c__Iterator.password = password;
    <Register>c__Iterator.password2 = password2;
    <Register>c__Iterator.email = email;
    <Register>c__Iterator.<$>name = name;
    <Register>c__Iterator.<$>password = password;
    <Register>c__Iterator.<$>password2 = password2;
    <Register>c__Iterator.<$>email = email;
    <Register>c__Iterator.<>f__this = this;
    return <Register>c__Iterator;
}

Here i get two error for every <Register> for using the < and > symbols and three errors for every <$> for using <, $ and > symbols. What do you think might cause these errors?

Answer 1

By the looks of things you are using an iterator block - a language featured introduced with C# 2.0.

Iterator blocks are syntactic sugar. When the compiler encounters an iterator block it will apply syntactic mapping which will expand the iterator block to become something more complicated internally. What you are looking at when you open your assembly in a disassembler is the product of syntactic mapping.

The compiler does not want you to be able to refer to this compiler generated code (as it would be confusing and potentially dangerous/conflicting) so it gives the generated identifiers unspeakable names that would otherwise be invalid in C#.

In summary, the <, > and $ symbols are invalid in C# but not in IL (which is what the disassembler will best-attempt to accurately reconstruct the source code from).