A, IS operator for determining whether an object can be converted to the specified type, no exception is thrown, bool return value to indicate whether the conversion is successful:
if (myObj is MyClass) { //do... }
When the conversion is successful meet any of the following circumstances:
1. Conversion object is an instance of the target type;
2. The conversion from the target object is an instance of a derived type type;
3. Conversion object is an implementation example of the type of the target interface;
Mode is supported in C # 7.0 or later and switch the match expression pattern matching expression;
Two, as operator with a similar cast, but will not throw an exception if the conversion is unsuccessful, it will return null, is usually used in conjunction with sentence air operations:
MyClass myObj = obj as MyClass; if (myObj != null) { //do... }
Only 1.as operator (if the original object and the target type is a value type is a reference type, the target type can be used to successfully convert a reference type or nullable type conversion operator, generally does not create new objects in the conversion will produce packing operation, a new object); for certain types of non-nullable type value types can be used with the cast is operator conversion:
if (myObj is int) { int myNum = (int)myObj; //do... }
※ generics, if required as operators convert the object type parameter type, it is necessary to add a base class or class type constraint constraints:
WHERE T: BaseClass // specify a base class constraints WHERE T: class // specified class type constraint
When 2.is as operator and will not perform a custom type conversion (in this case should use a cast), the type thereof only when the operation is switched in line with the target objects when the type conversion rules (i.e., above situations) to conversion successful;
※ compared to the cast, it should be used as much as possible as operator, since as operators convert safer and more efficient;
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Author: Minotauros
Source: https://www.cnblogs.com/minotauros/
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