Improve ASP.Net Performance by effective utilitzation of String

Many people ask me that how they can improve their website's performance? There are many ways through which you can improve the performance of your website but today, I will discuss the performance improvement with Strings.
In my opinion String is the most frequently used data type compared to other data types available. But there is a big problem with string, it is immutable. An immutable object is an object which cannot be modified. So whenever we try to change anything with string a new string object is created. These frequent creations of objects degrade the system's policy.

Avoid using "" as empty string

Every time when you write "" a new string object is created. But if you use string.Empty it will not create any additional string before assignment.
//bad practice
string str = "";

//good practice
string str1 = string.Empty;

Avoid .ToLower()/.ToUpper() for Comparison

Usually developers heavily use .ToLower() or .ToUpper() to perform case insensitive comparison. Instead you should use string.Compare function.
//Bad Practice
string errorCode= "ec-1001";
if (errorCode.ToLower() == "ec-1001")


//good Practice
string errorCode1 = "ec-1001";
if (string.Compare( errorCode1,"ec-1001",true)==0)

Also there are situations when we can control the case of a string i.e. generally we add 'M' or 'F' for gender. Now we can ensure that throughout application we either use capital 'M' or small 'm' to define male. A good approach is to use const in such cases.
const string Male = "M";
const string Female = "F";
string myGender = Male;

Avoid multiple string concatenation

Whenever you have to modify a string many times then consider using StringBuilder instead of simple string. Every time when you modify a string, a new object would be created. However, StringBuilder is mutable object and it performs string modifications without creating multiple objects.

//Bad practice
string text = "start";
text += "start 1";
text += "start 2";
text += "start 3";
text += "start 4";
text += "start 5";

for (int i = 0; i < 10; i++)
    text += "text " + i;

//Good Practice
StringBuilder sb = new StringBuilder();
sb.Append("start 2");
sb.Append("start 3");
sb.Append("start 4");
sb.Append("start 5");

for (int j = 0; j < 10; j++)
    sb.Append( "text " + j);