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Compiler Error CS0191

Property or indexer 'name' cannot be assigned to -- it is read only

A readonly field can only take an assignment in a constructor or at declaration. For more information, see Constructors (C# Programming Guide).

CS0191 also results if the readonly field is static and the constructor is not marked static.

The following sample generates CS0191.

// CS0191.cs
class MyClass
    public readonly int TestInt = 6;  // OK to assign to readonly field in declaration

        TestInt = 11; // OK to assign to readonly field in constructor

    public void TestReadOnly()
        TestInt = 19;                  // CS0191

    public static void Main()

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