CA1502Maintainability Enabled by default: No

Avoid excessive complexity

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

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

The rule reports a violation when the cyclomatic complexity of a method is more than 25. However, you can configure the threshold and also specify other kinds of symbols that the rule should analyze.

You can learn more about code metrics at Measure complexity of managed code.

Cause

A method has an excessive cyclomatic complexity.

How to fix violations

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

Example

public void Method()
{
    Console.WriteLine("Hello World!");
}

void Method(bool condition)
{
    if (condition)
    {
        Console.WriteLine("Hello World!");
    }
}

public void Method(bool condition1, bool condition2)
{
    if (condition1 || condition2)
    {
        Console.WriteLine("Hello World!");
    }
}

public void Method(DayOfWeek day)
{
    switch (day)
    {
        case DayOfWeek.Monday:
            Console.WriteLine("Today is Monday!");
            break;
        case DayOfWeek.Tuesday:
            Console.WriteLine("Today is Tuesday!");
            break;
        case DayOfWeek.Wednesday:
            Console.WriteLine("Today is Wednesday!");
            break;
        case DayOfWeek.Thursday:
            Console.WriteLine("Today is Thursday!");
            break;
        case DayOfWeek.Friday:
            Console.WriteLine("Today is Friday!");
            break;
        case DayOfWeek.Saturday:
            Console.WriteLine("Today is Saturday!");
            break;
        case DayOfWeek.Sunday:
            Console.WriteLine("Today is Sunday!");
            break;
    }
}

When to suppress

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. You might see false positive warnings from this rule if all of the following apply:

You're using Visual Studio 2022 version 17.5 or later with an older version of the .NET SDK, that is, .NET 6 or earlier.
You're using the analyzers from the .NET 6 SDK or an older version of the analyzer packages, such as Microsoft.CodeAnalysis.FxCopAnalyzers.

The false positives are due to a breaking change in the C# compiler. Consider using a newer analyzer that contains the fix for the false positive warnings. Upgrade to Microsoft.CodeAnalysis.NetAnalyzers version 7.0.0-preview1.22464.1 or newer or use the analyzers from the .NET 7 SDK.

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