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VB.NET Integer.Parse: Convert String to Integer

Convert Strings to Integers with the Integer.Parse and TryParse Functions.
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.

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

Version 1: This version of the code calls Convert.ToInt32 to convert the 4-character string to an Integer.

Version 2: This code uses Integer.Parse to perform the conversion. Like version 1, it should receive the Integer 1234.

VB.NET program that benchmarks Convert.ToInt32 Module Module1 Sub Main() Dim m As Integer = 100000 Dim text As String = "1234" ' Version 1: use Convert.ToInt32. Dim s1 As Stopwatch = Stopwatch.StartNew For i As Integer = 0 To m - 1 Dim result As Integer = Convert.ToInt32(text) Next s1.Stop() ' Version 2: use Integer.Parse. Dim s2 As Stopwatch = Stopwatch.StartNew For i As Integer = 0 To m - 1 Dim result As Integer = Integer.Parse(text) Next s2.Stop() Dim u As Integer = 1000000 Console.WriteLine(((s1.Elapsed.TotalMilliseconds * u) / m).ToString("0.00 ns")) Console.WriteLine(((s2.Elapsed.TotalMilliseconds * u) / m).ToString("0.00 ns")) End Sub End Module Output 79.19 ns Convert.ToInt32 76.20 ns Integer.Parse
Benchmark, invalid string. With Integer.TryParse we handle invalid strings much faster than with Integer.Parse. Consider this benchmark. We try to parse the string "xyz."

Version 1: The "A" function is called and the Integer.Parse method throws an Exception each time.

Exception

Version 2: The TryParse method is called. No exceptions are thrown. But the same result is returned.

Result: The Integer.TryParse method is many times faster than the Integer.Parse method when dealing with invalid string data.

VB.NET program that benchmarks invalid string parsing Module Module1 Sub Main() Dim m As Integer = 100000 Console.WriteLine(A()) Console.WriteLine(B()) Dim s1 As Stopwatch = Stopwatch.StartNew For i As Integer = 0 To m - 1 A() Next s1.Stop() Dim s2 As Stopwatch = Stopwatch.StartNew For i As Integer = 0 To m - 1 B() Next s2.Stop() Dim u As Integer = 1000000 Console.WriteLine(((s1.Elapsed.TotalMilliseconds * u) / m).ToString("0.00 ns")) Console.WriteLine(((s2.Elapsed.TotalMilliseconds * u) / m).ToString("0.00 ns")) End Sub Function A() As Integer ' Use Parse on an invalid string, but handle the exception. Dim result As Integer Try result = Integer.Parse("xyz") Catch ex As Exception result = 0 End Try Return result End Function Function B() As Integer ' Use TryParse on an invalid string. Dim result As Integer Integer.TryParse("xyz", result) Return result End Function End Module Output 0 0 23907.64 ns Integer.Parse, Try, Catch 49.87 ns Integer.TryParse
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.

Convert String, IntegerInteger

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

A recommendation. Integer.TryParse typically simplifies your code. Not only that, but it leads to more robust and crash-proof code. I typically recommend TryParse.
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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