In C#, a constant is a value that cannot be modified after it is declared. Constants are typically used for values that will not change throughout the execution of a program, such as mathematical constants or other unchanging values.
To declare a constant in C#, use the const keyword followed by the type and the name of the constant. The value of the constant must be specified at the time it is declared, and it cannot be modified later.
Here is an example of how to declare a constant in C#:
1 2 3 | const double PI = 3.14159; |
Note that constants must be initialized with a value when they are declared. They cannot be left uninitialized and given a value later.
It is also important to note that constants are considered to be compile-time values, which means that their value is determined at the time the program is compiled rather than at runtime. This means that constants can be used in place of literals in any context where a value is expected.
For example, the following code is valid because the constant PI is used in place of a literal value:
1 2 3 | double circumference = 2 * PI * radius; |
One important restriction on constants is that they can only be of one of the following types:
- A built-in integral type (
sbyte,byte,short,ushort,int,uint,long,ulong) - A built-in floating-point type (
float,double) - The
chartype - The
stringtype
In addition, constants cannot be of a user-defined type, such as a struct or a class.
It is generally good practice to use constants for values that will not change throughout the execution of a program, as it can make the code more readable and easier to maintain. Constants can also improve the performance of a program, as the compiler can optimize code that uses constants more effectively than code that uses variables.
