1. is to verify whether the operation object is what you want
Operation formula: Object is type
Return true: The object is the specified type
Return false: The object is not the specified type
2. as is to convert the object to the specified type
Operation formula: object as type
Conversion successfully: The type of the object is the specified type
Conversion failed: Return null
Note: The "is" and "as" operator must be used with a reference type or nullable type (example: 'int' is a non-nullable value type)