Explain the difference between String and string in C#. Are they interchangeable?

String and string

In C#, String and string both represent the same type: the .NET System.String class. They are functionally identical and interchangeable, but they are used in slightly different contexts depending on coding conventions and readability.

Technical Explanation

• string: This is a C# keyword that acts as an alias for the System.String class in the .NET Framework. It is primarily used for declaring variables and method parameters.
• String: This is the actual .NET type, fully qualified as System.String. It provides access to all methods and properties defined in the String class.

For Example:

string myString = "Hello";
String anotherString = "World";

Both lines create a System.String object, and the two terms are interchangeable.

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When to Use Each

Use string:

• When declaring variables, properties, or method parameters and return types.
• It aligns with C# coding conventions and enhances readability.

string name = "John";

Use String:

• When accessing static members of the System.String class directly.
• It makes the connection to the .NET class explicit, which is useful for clarity in some cases.

string emptyString = String.Empty;

Interchangeability

Yes, they are interchangeable in functionality. Whether you use string or String, the behavior and performance remain identical. The choice depends on readability and coding style preferences.