Design limitations of structure type (struct)

Structure ​ Less used in the development process , If it is C# call C++ The related functions of may pass parameters with the help of structures , Understand the relevant knowledge of structure , It helps us to better use the structure .

One 、 Design structure (struct) Type , Have and classes (class) Functions of the same type , But there are the following exceptions ：

• You cannot declare a parameterless constructor . Each structure type already provides an implicit parameterless constructor , This constructor generates the default value of the type .  Remarks from C# 10 Start , You can declare a parameterless constructor in a structure type . For more information , See the parameterless constructor and field initializer section .
• You cannot initialize instance fields or properties when they are declared . however , Static or constant fields or static attributes can be initialized in their declarations .  Remarks from C# 10 Start , You can initialize instance fields or attributes when they are declared . For more information , See the parameterless constructor and field initializer section .
• The constructor of a structure type must initialize all instance fields of that type .
• Structure types cannot inherit from other classes or structure types , Nor can it be used as the basic type of a class . however , Structure types can implement interfaces .
• Finalizers cannot be declared in a structure type .

Two 、​ Structure (struct) With C# The version upgrade is also iterating continuously .

• from C# 7.2 Start , have access to readonly Modifier to declare the structure type as immutable .
• from C# 7.2 Start , It can be used in the declaration of structure type ref Modifier .
• stay C# 8.0 And later , This means that instance members other than constructors are implicit readonly.
• from C# 8.0 Start , One time can be defined ref structure .
• from C# 8.0 Start , You can also use readonly Modifier declares that instance members will not modify the state of the structure .
• stay C# 9.0 And later , Can be readonly Modifier applied to have init Accessor properties or indexers .
• from C# 10 Start , have access to with Expression to generate a copy of the structure type instance that modifies the specified properties and fields .
• from C# 10 Start , You can declare a parameterless constructor in a structure type .
• from C# 10 Start , You can initialize instance fields or attributes when they are declared .