IndexOf function should check the first character

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Metadata

ID: csharp-best-practices/indexof-checks

Language: C#

Severity: Warning

Category: Error Prone

Description

When using Indexof or LastIndexOf, using > 0 may miss the first item of the collection (string, list, etc). Instead, the code should use >=0 to take the first element into account.

Non-Compliant Code Examples

using System.Net;

class MyClass {
    public static void routine(string str, string str2)
    {
        str.IndexOf(str2)>0;
        str.IndexOf(str2)>0;
        str.LastIndexOf(str2)>0;
    }
}

Compliant Code Examples

using System.Net;

class MyClass {
    public static void routine(string str, string str2)
    {
        str.IndexOf(str2)>=0;
        str.IndexOf(str2)>=0;
        str.LastIndexOf(str2)>=0;
        if (serverPackages.Any(x => x.Version.CompareTo(currentVersion) > 0)) {
            
        }
    }
}