4.3. Type Conversion

Sometimes it is necessary to convert values from one type to another. A common example is when a program receives input from a user or a file. In this situation, numeric data may be passed to the program as strings and your code is looking for a double data type, not string.

C# provides a few simple methods that will allow us to convert values to different data types. The methods Int32.Parse and Double.Parse will (attempt to) convert their arguments into types int and double, respectively. We call these type conversion functions.

The Int32.Parse method can take a string and convert it into an integer whilte Double.Parse converts strings into a double. Let’s see this in action:

Example

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Console.WriteLine(Int32.Parse("2345"));
Console.WriteLine((Int32.Parse("2345")).GetType());
Console.WriteLine(Double.Parse("17"));
Console.WriteLine((Double.Parse("17.8")).GetType());

Console Output

2345
System.Int32
17
System.Double

What happens if we attempt to convert a string to a number, and the string doesn’t directly represent a number?

Example

Console.WriteLine(Int32.Parse("23bottles"));

Console Output

Unhandled Exception: System.FormatException: Input string was not in a correct format.

This example shows that a string has to be a syntactically legal number for conversion to go as expected. Examples of such strings are "34" or "-2.5". If the value cannot be cleanly converted to a number then an error will be returned.

Converting other data types into strings is more complex than a simple parse. We will return back to this concept once we learn more about strings.

4.3.1. Check Your Understanding

Question

Which of the following will result in Double.System when passed to GetType?

  1. '3'
  2. 'three'
  3. 3.3333
  4. 33