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Optimizing C# Application


7 Ways To Optimize C# Code

Code optimization is an important aspect of writing an efficient C# application. The following tips will help you increase the speed and efficiency of your C# code and applications.

1. Knowing when to use StringBuilder

You must have heard before that a StringBuilder object is much faster at appending strings together than normal string types.

The thing is StringBuilder is faster mostly with big strings. This means if you have a loop that will add to a single string for many iterations then a StringBuilder class is definitely much faster than a string type.

However if you just want to append something to a string a single time then a StringBuilder class is overkill. A simple string type variable in this case improves on resources use and readability of the C# source code.

Simply choosing correctly between StringBuilder objects and string types you can optimize your code.

2. Comparing Non-Case-Sensitive Strings

In an application sometimes it is necessary to compare two string variables, ignoring the cases. The tempting and traditionally approach is to convert both strings to all lower case or all upper case and then compare them, like such:

str1.ToLower() == str2.ToLower()

However repetitively calling the function ToLower() is a bottleneck in performace. By instead using the built-in string.Compare() function you can increase the speed of your applications.

To check if two strings are equal ignoring case would look like this:

string.Compare(str1, str2, true) == 0 //Ignoring cases

The C# string.Compare function returns an integer that is equal to 0 when the two strings are equal.

3. Use string.Empty

This is not so much a performance improvement as it is a readability improvement, but it still counts as code optimization. Try to replace lines like:

if (str == "")


if (str == string.Empty)

This is simply better programming practice and has no negative impact on performance.

Note, there is a popular practice that checking a string's length to be 0 is faster than comparing it to an empty string. While that might have been true once it is no longer a significant performance improvement. Instead stick with string.Empty.

4. Replace ArrayList with List<>

ArrayList are useful when storing multiple types of objects within the same list. However if you are keeping the same type of variables in one ArrayList, you can gain a performance boost by using List<> objects instead.

Take the following ArrayList:

ArrayList intList = new ArrayList();
return (int)intList[0] + 20;

Notice it only contains intergers. Using the List<> class is a lot better. To convert it to a typed List, only the variable types need to be changed:

List<int> intList = new List<int>();
return intList[0] + 20;

There is no need to cast types with List<>. The performance increase can be especially significant with primitive data types like integers.

5. Use && and || operators

When building if statements, simply make sure to use the double-and notation (&&) and/or the double-or notation (||), (in Visual Basic they are AndAlso and OrElse).

If statements that use & and | must check every part of the statement and then apply the "and" or "or". On the other hand, && and || go thourgh the statements one at a time and stop as soon as the condition has either been met or not met.

Executing less code is always a performace benefit but it also can avoid run-time errors, consider the following C# code:

if (object1 != null && object1.runMethod())

If object1 is null, with the && operator, object1.runMethod()will not execute. If the && operator is replaced with &, object1.runMethod() will run even if object1 is already known to be null, causing an exception.

6. Smart Try-Catch

Try-Catch statements are meant to catch exceptions that are beyond the programmers control, such as connecting to the web or a device for example. Using a try statement to keep code "simple" instead of using if statements to avoid error-prone calls makes code incredibly slower. Restructure your source code to require less try statements.

7. Replace Divisions

C# is relatively slow when it comes to division operations. One alternative is to replace divisions with a multiplication-shift operation to further optimize C#. The article explains in detail how to make the conversion.


As you can see these are very simple C# code optimizations and yet they can have a powerful impact on the performance of your application. To test out the optimizations, try out the free Optimizing Utility.


An important concept when it comes to increasing the speed and efficiency of you C# code, is code profiling. A good profiler can not only let you know about the speed bottlenecks in your applications, but it can also help you with memory management. The best .NET profiler is probably RedGates ANTS Profiler. They have a free trial at their homepage you can download before purchasing the full product.

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