What is the Difference between String and string in C#?

According to MSDN ,string is an alias for String in the .NET Framework.Despite C# being a case-sensitive language you can see, whether you use “string” or “String,” the outcome is the same.

In simple, there is no difference between string and String. string is a alias created by Microsoft for System.String.

As we go into details, you can see these difference between them:

• A String object is called immutable (read-only) because its value cannot be modified once it has been created. Methods that appear to modify a String object actually return a new String object that contains the modification. If it is necessary to modify the actual contents of a string-like object
• string' is the intrinsic C# datatype, and is an alias for the system provided type "System.String". The C# specification states that as a matter of style the keyword ('string') is preferred over the full system type name (System.String, or String).
• use String when using the static methods on the String class, like String.Split() or String.IsNullOrEmpty()
• use string to declare types - variables, properties, return values and parameters. This is consistent with the use of other system types - int, bool, var etc (although Int32 and Boolean are also correct).

"string" keyword is an alias for System.String in the .NET, that means the String and string are equal, you can either one of them while writing code in C#

Syetem.String and string are compiled to System.String in Intermediate Language (IL), so the performance of both is also same, it just depends on your choice, which one to use.

• Use string while referring to an object.
• Use String while referring to the class.