#519 – Differences Between structs and classes

There are a number of differences between a struct and a class, including:

  • A struct is a value type (instance created on the stack); a class is a reference type (instance created on the heap)
  • A variable defined as a struct type contains the actual data in the struct; a variable defined as a class type references or points to the data stored in the instance of the class
  • Memory for a struct is released when its variable goes out of scope; memory for a class instance is released when the object is garbage collected
  • When a struct is assigned to a new variable, a copy is made (changes to the original are not reflected in the copy); when an instance of a class is assigned to a new variable, the new variable references the existing instance
  • When a struct is passed to a method, a copy is made
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About Sean
Software developer in the Twin Cities area, passionate about .NET technologies. Equally passionate about my own personal projects related to family history and preservation of family stories and photos.

One Response to #519 – Differences Between structs and classes

  1. Ralph Burton says:

    When a struct is passed to a method, a copy is made,
    unless a reference to it is passed using either the “ref” or “out” qualifiers.

    public struct struct_type
    { public int x1; }

    public void foo_77 (out struct_type p_a_struct)
    { p_a_struct.x1 = 77; }

    public void foo_99 (ref struct_type p_a_struct)
    { p_a_struct.x1 = 99; }

    struct_type struct_1;
    foo_77 (out struct_1);

    struct_type struct_2;
    struct_2.x1 = 88;
    foo_99 (ref struct_2);

    // struct_1.x1 = 77

    // struct_2.x1 = 99

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