# Avoid excessive complexity

Visual Studio 2008

 TypeName AvoidExcessiveComplexity CheckId CA1502 Category Microsoft.Maintainability Breaking Change Non Breaking

## Cause

A method has an excessive cyclomatic complexity.

## Rule Description

Cyclomatic complexity measures the number of linearly independent paths through the method, which is determined by the number and complexity of conditional branches. A low cyclomatic complexity generally indicates a method that is easy to understand, test, and maintain. The cyclomatic complexity is calculated from a control flow graph of the method and is given as follows:

cyclomatic complexity = the number of edges - the number of nodes + 1

where a node represents a logic branch point and an edge represents a line between nodes.

The rule reports a violation when the cyclomatic complexity is more than 25.

## How to Fix Violations

To fix a violation of this rule, refactor the method to reduce its cyclomatic complexity.

## When to Suppress Warnings

It is safe to suppress a warning from this rule if the complexity cannot easily be reduced and the method is easy to understand, test, and maintain. In particular, a method that contains a large switch (Select in Visual Basic) statement is a candidate for exclusion. The risk of destabilizing the code base late in the development cycle or introducing an unexpected change in runtime behavior in previously shipped code might outweigh the maintainability benefits of refactoring the code.

## How Cyclomatic Complexity is Calculated

Basically, the cyclomatic complexity is calculated by adding 1 to the following:

• Number of branches (such as if, while, and do)

• Number of case statements within a switch

The following examples show methods with varying cyclomatic complexities.

## Example

Cyclomatic Complexity of 1

```Public Sub Method()
Console.WriteLine("Hello World!")
End Sub
```

Cyclomatic Complexity of 2

```Public Sub Method(ByVal condition As Boolean)
If (condition) Then
Console.WriteLine("Hello World!")
End If
End Sub
```

Cyclomatic Complexity of 3

```Public Sub Method(ByVal condition1 As Boolean, ByVal condition2 As Boolean)
If (condition1 OrElse condition2) Then
Console.WriteLine("Hello World!")
End If
End Sub
```

Cyclomatic Complexity of 8

```Public Sub Method(ByVal day As DayOfWeek)
Select Case day
Case DayOfWeek.Monday
Console.WriteLine("Today is Monday!")
Case DayOfWeek.Tuesday
Console.WriteLine("Today is Tuesday!")
Case DayOfWeek.Wednesday
Console.WriteLine("Today is Wednesday!")
Case DayOfWeek.Thursday
Console.WriteLine("Today is Thursday!")
Case DayOfWeek.Friday
Console.WriteLine("Today is Friday!")
Case DayOfWeek.Saturday
Console.WriteLine("Today is Saturday!")
Case DayOfWeek.Sunday
Console.WriteLine("Today is Sunday!")
End Select
End Sub
```