What is the difference between explicit and implicit?

Before figuring out the differences between the two keywords, you need to figure out another Keyword: operator.

Operator msdn explanation:

UseOperatorKeyword to overload the built-in operators, or provide user-defined conversions in the class or structure declaration.

That is to say: operator has two functions: 1) Operator Overloading 2) Conversion of user-defined classes, that is, operator conversion.

Here we only talk about operator conversion. For example, I have defined the following class (the code is from msdn)

 

Class Digit

{

Public digit (double D) {val = D ;}

Public double val;

//... Other members

 

}

 

If I want to convert the digit class to the dobule type, that is

Digit dig = 12; certainly, an error is reported because conversion from double to digit is not defined here. It is defined as follows:

 

Class Digit

{

Public digit (double D) {val = D ;}

Public double val;

//... Other members

 

// User-Defined conversion from digit to double

Public Static Implicit operator double (digit D)

{

Return D. Val;

}

// User-Defined conversion from double to Digit

Public Static Implicit operator digit (double D)

{

Return new digit (d );

}

 

}

No error will be reported, because the conversion from double to digit operator is defined here:

Public Static Implicit operator digit (double D)

 

 

{

Return new digit (d );

}

In turn, explicit and implicit

Explicit is the type conversion of the display. If the double operator is defined in this way

// User-Defined conversion from digit to double

Public static explicit operator double (digit D)

{

Return D. Val;

}

 

 

Double num = dig.

Convert a digit type to a double type

 

 

Double num = (double) Dig;