C# foreach improvements

I think you should stick with the conventions that your co-workers are used to. The principle of least surprise. You don't want to sit and figure out why a simple operation is written in an uncommon manner for no reason, so why should the next guy who is reading your code?

I think a good reason is that in every other case, the scope of a “normal” local variable is a block delimited by braces ({}). The local variables that are not normal appear in a special construct before a statement (which is usually a block), like a for loop variable or a variable declared in using.

One more exception are local variables in LINQ query expressions, but those are completely different from normal local variable declarations, so I don't think there is a chance of confusion there.

For reference, the rules are in §3.7 Scopes of the C# spec:

• The scope of a local variable declared in a local-variable-declaration is the block in which the declaration occurs.

• The scope of a local variable declared in a switch-block of a switch statement is the switch-block.

• The scope of a local variable declared in a for-initializer of a for statement is the for-initializer, the for-condition, the for-iterator, and the contained statement of the for statement.

• The scope of a variable declared as part of a foreach-statement, using-statement, lock-statement or query-expression is determined by the expansion of the given construct.

(Though I'm not completely sure why is the switch block explicitly mentioned, since it doesn't have any special syntax for local variable declations, unlike all the other mentioned constructs.)