VB.NET Integer.Parse, TryParse: Convert String to Integer

Integer.Parse. A String sometimes contains digits.

It is converted to an Integer in VB.NET with Integer.Parse. This is a powerful function.

Several Functions. There are several Integer parsing Functions in the .NET Framework. We see methods and tips for converting Strings to Integers.

First example. We see a simple example that converts a String containing digits into an actual Integer value. An Integer is often more convenient for a program.

Here: We declare a String with the contents "42." This is not an Integer, but a representation of two digits in character form.

Result: Integer.Parse receives the text string and returns the Integer form of it.

Based on:

.NET 4.5

VB.NET program that uses Integer.Parse

Module Module1
    Sub Main()
	' Your input string.
	Dim text As String = "42"

	' Convert string to integer value.
	Dim value As Integer = Integer.Parse(text)

	' Write output.
	Console.WriteLine(value)
    End Sub
End Module

Output

42

Integer.TryParse. This is a programmatic way to both test for integers and parse them in a single pass. When parsing integers, we want to avoid exceptions and gracefully handle errors.

Therefore: To accomplish this, we use the Integer.TryParse shared method. TryParse provides a tester-doer pattern to parsing.

Here: This example calls the Integer.TryParse function, which will not throw an exception if the input string is invalid.

Instead: It will return false. The example further shows how to test the return value of TryParse.

VB.NET program that uses TryParse

Module Module1
    Sub Main()
	' An invalid number string.
	Dim s As String = "x"

	' Try to parse it.
	' ... If it isn't a number, use -1.
	Dim num As Integer
	If Not Integer.TryParse(s, num) Then
	    num = -1
	End If

	' Writes -1 to the screen.
	Console.WriteLine(num)
    End Sub
End Module

Output

-1

Using TryParse. This approach typically simplifies your code. Not only that, but it leads to more robust and crash-proof code. I typically recommend TryParse.

ToInt32. Here we use Convert.ToInt32 to convert a String to an int. Internally, Convert.ToInt32 is implemented with Integer.Parse. It throws on invalid input.

And: The String is converted to an Integer, in the same way as with Integer.Parse. The Integer 500 is written to the Console here.

Console.Write

VB.NET program that uses Convert.ToInt32

Module Module1
    Sub Main()
	' The input string you want to convert to Integer.
	Dim text As String = "500"

	' Convert to an Integer.
	Dim value As Integer = Convert.ToInt32(text)

	' Writes 500 to screen.
	Console.WriteLine(value)
    End Sub
End Module

Output

500

Benchmark. Convert.ToInt32 is slower than a call to Integer.Parse. This is because it contains some branch instructions and also has extra method invocation.

Next: To demonstrate, this benchmark times a call to Convert.ToInt32 and Integer.Parse.

Sample that uses Convert.ToInt32: VB.NET

Dim text As String = "1234"
Dim i As Integer = Convert.ToInt32(text)

Sample that uses Integer.Parse: VB.NET

Dim text As String = "1234"
Dim i As Integer = Integer.Parse(text)

Benchmark result, 10 million iterations

138.53 ns
126.76 ns

Exceptions. Here we see what happens when you try to parse a String that does not contain a numeric value as an Integer. You will get a System.FormatException.

Invalid: This exception simply means that Integer.Parse was passed a String in an invalid format.

Tip: We can handle this problem with exception-handling. But for performance it is better to use Integer.TryParse.

VB.NET program that catches Parse Exception

Module Module1
    Sub Main()
	' First entry try block.
	Try
	    ' Parses invalid string and throws.
	    Dim x As String = "bad"
	    Dim y As Integer = Integer.Parse(x)
	Catch ex As Exception
	    ' Write exception to screen.
	    Console.WriteLine(ex)
	End Try
    End Sub
End Module

Output

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

Tester-doer. This pattern is used for TryParse. First, the code sees if the parsing will succeed. If this test succeeds, it will do the parse. This avoids costly exceptions.

Integer: Sometimes code that uses Strings where Integers are better. We can convert Strings that contain Integers to actual Integers.

Integer

And: This can improve compatibility. It can lead to improved error-checking. Integers are easier to test.

Parse examples. Integer.Parse and TryParse are helpful. These functions are the most important and widely-used ones for converting integers to strings.

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