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The difference is that the value of a static readonly field is set at run time, and can thus be modified by the containing class, whereas the value of a const field is set to a compile time constant.
In the static readonly case, the containing class is allowed to modify it only
static readonly is typically used if the type of the field is not allowed in a const declaration, or when the value is not known at compile time.
Instance readonly fields are also allowed.
Remember that for reference types, in both cases (static and instance) the readonly modifier only prevents you from assigning a new reference to the field. It specifically does not make immutable the object pointed to by the reference.
public static readonly Test test = new Test();
static void Main(string args)
test.Name = "Program";
test = new Test(); // Error: A static readonly field cannot be assigned to (except in a static constructor or a variable initializer)
public string Name;
On the other hand, if Test were a value type, then assignment to test.Name would be an error.
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dIFFERENCE bETWEEN // and / in C# when using url
Nice article, I've also wrote an article about that context.
It can be found here:
The readonly keyword is different from the const keyword. A const field can only be initialized at the declaration of the field. A readonly field can be initialized either at the declaration or in a constructor. Therefore, readonly fields can have different values depending on the constructor used. Also, while a const field is a compile-time constant, the readonly field can be used for runtime constants
I need practical example which scenario we really need read only variable or class.