Why is this an issue?

Methods with a long parameter list are difficult to use, as maintainers must figure out the role of each parameter and keep track of their position.

void SetCoordinates(int x1, int y1, int z1, int x2, int y2, int z2) // Noncompliant
{
   // ...
}

The solution can be to:

• Split the method into smaller ones

// Each function does a part of what the original setCoordinates function was doing, so confusion risks are lower
void SetOrigin(int x, int y, int z)
{
   // ...
}

void SetSize(int width, int height, int depth)
{
   //
}

• Find a better data structure for the parameters that group data in a way that makes sense for the specific application domain

// In geometry, Point is a logical structure to group data
readonly record struct Point(int X, int Y, int Z);

void SetCoordinates(Point p1, Point p2)
{
    // ...
}

This rule raises an issue when a method has more parameters than the provided threshold.

Exceptions

The rule does not count the parameters intended for a base class constructor.

With a maximum number of 4 parameters:

public class BaseClass
{
    public BaseClass(int param1)
    {
        // ...
    }
}

public class DerivedClass : BaseClass
{
    public DerivedClass(int param1, int param2, int param3, string param4, long param5) : base(param1) // Compliant by exception
    {
        // ...
    }
}