Usage and difference of As and is in C #

I. type conversion

1. Any type can be converted to its base class type, which is completed by implicit conversion;

2. Display conversion is required when any type is converted to its derived type. For example: (type name) Object Name;
3. Use GetType to obtain the exact type of any object;

4. You can use the convert class to convert basic types;
5. All types except string have the parse method, which is used to convert the string type to the corresponding basic type;

6. The conversion between the value type and the reference type is called boxing or unboxing );

2. is/as Example

Is conversion rules:

1. Check the compatibility of object types and return true (false );
2. No exception is thrown;
3. If the object is null, false is returned;

Example:

C # Code

2. ObjectO ="ABC";
4. If(OIs String)// Perform the first type compatibility check
   
6. {
8. StringS = (String) O;// Perform the second type compatibility check and convert
10. MessageBox. Show ("Conversion successful! ");
    
12. }
14. Else
16. {
18. MessageBox. Show ("Conversion failed! ");
    
20. }

Object o = "ABC"; if (O is string) // perform the first type compatibility check {string S = (string) O; // perform the second type compatibility check, and convert MessageBox. show ("conversion successful! ");} Else {MessageBox. Show (" Conversion failed! ");}
 

As conversion rules:

1. Check the compatibility of object types and return the conversion result. If not, null is returned;
2. No exception is thrown;

3. If the result is null, an nullreferenceexception exception will be thrown during forced type conversion;

Example:

C # code

1. Object O = "ABC" ;
2. string S = O as string ; // executes the first type compatibility check and returns the result.
3. If (s! = null )
4. MessageBox. Show ( "conversion successful! " );
   
5. else
6. MessageBox. Show ( "Conversion failed! " );

Object o = "ABC"; string S = O as string; // execute the first type compatibility check and return the result if (s! = NULL) MessageBox. Show ("conversion successful! "); Else MessageBox. Show (" Conversion failed! ");
 

Note: As performs a compatibility check less than is, and the performance may be slightly higher.