Question

Consider the following code sample:

private void AddEnvelope(MailMessage mail)
{
    if (this.CopyEnvelope)
    {
        // Perform a few operations
    }
}

vs

private void AddEnvelope(MailMessage mail)
{
    if (!this.CopyEnvelope) return;
    // Perform a few operations
}

Will the bottom code execute any faster? Why would ReSharper make this recommendation?

Update

Having thought about this question the answer might seem obvious to some. But lots of us developers were never in the habit of nesting zounds of if statements in the first place…

Answer 1

Updated Answer:

It’s a code maintainability suggestion. Easier to read than nesting the rest of the code in an IF statement. Examples/discussion of this can be seen at the following links:

• Flattening Arrow Code
• Replace Nested Conditional With Guard Clauses
• Code Contracts section “Legacy Requires Statements”

Original Answer:

It will actually run (very negligibly) slower from having to perform a
NOT operation.

So much in fact, some people actually consider that prettier way to
code as it avoids an extra level of indentation for the bulk of the
code.