Checks for always-true expressions on collections and arrays

Documentos > Code Analysis > Static Analysis Rules > Checks for always-true expressions on collections and arrays

This page is not yet available in Spanish. We are working on its translation.
If you have any questions or feedback about our current translation project, feel free to reach out to us!

Metadata

ID: csharp-best-practices/unnecessary-length-count-check

Language: C#

Severity: Warning

Category: Best Practices

Description

Because the Length of an array or Count of a collection will never be negative, some expressions will always evaluate to true, and some will always evaluate to false.

if (collection.Count >= 0) { /* ... */ }
// Equivalent to
if (true) { /* ... */ }

if (arr.Length < 0) { /* ... */ }
// Equivalent to
if (false) { /* ... */ }

This rule warns when always-true or always-false expressions are detected.

Non-Compliant Code Examples

using System.Collections.Generic;
using static System.Linq.Enumerable;

class NonCompliant {
    public static void Main()
    {
        List<char> collection = ['a', 'b', 'c'];
        if (collection.Count >= 0) { /* ... */ }
        if (collection.Count >= 0b0) { /* ... */ }
        if (collection.Count >= 0x0) { /* ... */ }
        if (collection.Count >= -1) { /* ... */ }
        if (collection.Count > -1) { /* ... */ }
        if (collection.Count < 0) { /* ... */ }
        if (collection.Count < -1) { /* ... */ }
		
        char[] array = ['a', 'b', 'c'];
        if (array.Count() >= 0) { /* ... */ }
        if (array.Count() >= 0b0) { /* ... */ }
        if (array.Count() >= 0x0) { /* ... */ }
        if (array.Count() >= -1) { /* ... */ }
        if (array.Count() > -1) { /* ... */ }
        if (array.Count() < 0) { /* ... */ }
        if (array.Count() < -1) { /* ... */ }

        if (array.LongCount() >= 0b0) { /* ... */ }
        if (array.LongCount() >= 0x0) { /* ... */ }
        if (array.LongCount() >= -1) { /* ... */ }
        if (array.LongCount() > -1) { /* ... */ }
        if (array.LongCount() < 0) { /* ... */ }
        if (array.LongCount() < -1) { /* ... */ }

        if (array.Length >= 0) { /* ... */ }
        if (array.Length >= 0b0) { /* ... */ }
        if (array.Length >= 0x0) { /* ... */ }
        if (array.Length >= -1) { /* ... */ }
        if (array.Length > -1) { /* ... */ }
        if (array.Length < 0) { /* ... */ }
        if (array.Length < -1) { /* ... */ }
    }
}

Compliant Code Examples

using System.Collections.Generic;
using static System.Linq.Enumerable;

class Compliant {
    public static void Main()
    {
        List<char> collection = ['a', 'b', 'c'];
        if (collection.Count > 0) { /* ... */ }
        if (collection.Count > 0b0) { /* ... */ }
        if (collection.Count > 0x0) { /* ... */ }
        if (collection.Count > 1) { /* ... */ }
        if (collection.Count == 0) { /* ... */ }
		
        char[] array = ['a', 'b', 'c'];
        if (array.Count() > 0) { /* ... */ }
        if (array.Count() > 0b0) { /* ... */ }
        if (array.Count() > 0x0) { /* ... */ }
        if (array.Count() > 1) { /* ... */ }
        if (array.Count() == 0) { /* ... */ }

        if (array.LongCount() > 0) { /* ... */ }
        if (array.LongCount() > 0b0) { /* ... */ }
        if (array.LongCount() > 0x0) { /* ... */ }
        if (array.LongCount() > 1) { /* ... */ }
        if (array.LongCount() == 0) { /* ... */ }

        if (array.Length > 0) { /* ... */ }
        if (array.Length > 0b0) { /* ... */ }
        if (array.Length > 0x0) { /* ... */ }
        if (array.Length > 1) { /* ... */ }
        if (array.Length == 0) { /* ... */ }
    }
}