Type conversion is a process where data of one type is converted into data of another type (Docs, 2015). C# has 2 forms of type conversions:

1. implicit conversions
2. explicit conversions (or type casting)

Implicit conversions

The conversions are performed by C# in a type-safe manner, most of which are widening conversion.

For example, conversions

1. from smaller to larger integral types
2. from derived classes to base classes

from smaller to larger integral types

int num1 = 10;
double num2 = num1;

from derived classes to base classes

Derived d = new Derived();
Base b = d;

Explicit type conversion

Casting is required when information might be lost in the conversion, which is also known as a narrowing conversion. Explicit conversions require a cast operator in the form of (<target_type>)<data>.

For example, conversions

1. from larger to smaller integral types
2. from base class to child class

from larger to smaller integral types

double num1 = 10;
// int num2 = num1; // error
int num2 = (int)num1;

from base class to child class

Derived d = new Derived();
Base b = d;

// Derived d2 = b; // error
Derived d2 = (Derived)b;

References

1. Docs, M. (2015, July 20). Casting and Type Conversions (C# Programming Guide). Retrieved from https://docs.microsoft.com/en-us/dotnet/csharp/programming-guide/types/casting-and-type-conversions