Checks for always-true expressions on collections and arrays

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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) { /* ... */ }
    }
}