is it faster to reference a textbox's text property for a test or assign a string to the property then test?

I've been wondering which is faster (or if it even makes a difference), referencing a textbox's Text property or a string assigned to that value? Ref textbox.Text

if(textbox1.Text == "A")
{ //do a million iterations
}

Or

string aString = text开发者_运维百科box1.Text;
if(aString == "A")
{ //do a million iterations
}

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I made just a quick analyze using stop watch: 10.000.000 iterations.

In first case it returns to me: 00:00:21.56

In second case it returns to me: 00:00:42.62

In second case you have Get accessor + new pointer to string every iteration, so its slower.

Hope this helps.

EDIT

I put all code of any case inside the iteration. Seems that is the quetion.

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I don't think it will make any difference if compiler optimisation is on, but you could test this. Simply repeat the code a couple of million times with a StopWatch class to measure the timing of the total operation.

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I think the second option is faster. Reading the property is executing a function which reads the value of the textbox. There is a chance it gets optimized away, on the other hand there may be also a chance the value changes while the loop is executing so it needs to check it every time the property is read.