Question

In a for-loop in C#, which of the following codeblocks are the best performance wise? Or is there no difference?
The diffenrence is whether the condition is saved in a local variable or read directly from an object.

Option 1

float maxDepth = 0;
int maxnumber = 0;

for (int i = 0; i < defects.Total; i++)
{
    if (defects[i].Depth > maxDepth)
    {
        maxDepth = defects[i].Depth;
        maxnumber = i;
    }
}

Option 2

float maxDepth = 0;
int maxnumber = 0

int defectNumber = defects.Total;
for (int i = 0; i < defectNumber; i++)
{
    if (defects[i].Depth > maxDepth)
    {
        maxDepth = defects[i].Depth;
        maxnumber = i;
    }
}

I’m sorry if this question have been asked a lot, but I couldn’t find it anywhere.

Anders

Answer 1

For all such questions you can use System.Diagnostics.Stopwatch like this.

var stopwatch = new Stopwatch();
stopwatch.Start();

float maxDepth = 0; 
int maxnumber = 0;  
for (int i = 0; i < defects.Total; i++) 
{    
    if (defects[i].Depth > maxDepth)     
    {         
        maxDepth = defects[i].Depth;         
        maxnumber = i;     
    } 
} 

stopwatch.Stop();
Debug.WriteLine("Elapesed time for method 1: {0} msec.", stopwatch.ElapsedMilliseconds);
stopwatch.Reset();
stopwatch.Start();

maxDepth = 0; 
maxnumber = 0;  
int defectNumber = defects.Total; 
for (int i = 0; i < defectNumber; i++)     
{    
    if (defects[i].Depth > maxDepth)     
    {         
        maxDepth = defects[i].Depth;         
        maxnumber = i;     
    } 
} 
stopwatch.Stop();
Debug.WriteLine("Elapesed time for method 2: {0} msec.", stopwatch.ElapsedMilliseconds);

Then you got exact information. (The best way is to take several runs and use the mean value)