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Showing content from https://docs.microsoft.com/en-us/dotnet/fundamentals/code-analysis/quality-rules/ca1827 below:

CA1827: Do not use Count/LongCount when Any can be used (code analysis) - .NET

Property Value Rule ID CA1827 Title Do not use Count()/LongCount() when Any() can be used Category Performance Fix is breaking or non-breaking Non-breaking Enabled by default in .NET 9 As suggestion Cause

The Count() or LongCount() method was used where the Any() method would be more efficient.

Rule description

This rule flags Count() and LongCount() LINQ method calls that are used to check if the collection has at least one element. These methods enumerate the entire collection to compute the count. The same check is faster with the Any() method as it avoids enumerating the collection.

How to fix violations

To fix a violation, replace the Count or LongCount method call with the Any method. For example, the following two code snippets show a violation of the rule and how to fix it:

using System.Collections.Generic;
using System.Linq;

class C
{
    public string M1(IEnumerable<string> list)
        => list.Count() != 0 ? "Not empty" : "Empty";

    public string M2(IEnumerable<string> list)
        => list.LongCount() > 0 ? "Not empty" : "Empty";
}

using System.Collections.Generic;
using System.Linq;

class C
{
    public string M1(IEnumerable<string> list)
        => list.Any() ? "Not empty" : "Empty";

    public string M2(IEnumerable<string> list)
        => list.Any() ? "Not empty" : "Empty";
}

Tip

A code fix is available for this rule in Visual Studio. To use it, position the cursor on the violation and press Ctrl+. (period). Choose Do not use Count() or LongCount() when Any() can be used from the list of options that's presented.

When to suppress warnings

It's safe to suppress a violation of this rule if you're not concerned about the performance impact from unnecessary collection enumeration to compute the count.

Suppress a warning

If you just want to suppress a single violation, add preprocessor directives to your source file to disable and then re-enable the rule.

#pragma warning disable CA1827
// The code that's violating the rule is on this line.
#pragma warning restore CA1827

To disable the rule for a file, folder, or project, set its severity to none in the configuration file.

[*.{cs,vb}]
dotnet_diagnostic.CA1827.severity = none

For more information, see How to suppress code analysis warnings.