FirstHalfAnalyzer.cs

[DiagnosticAnalyzer(LanguageNames.CSharp)]
public class Analyzer1Analyzer : DiagnosticAnalyzer
{
    public const string DiagnosticId = "Analyzer1";

    // You can change these strings in the Resources.resx file. If you do not want your analyzer to be localize-able, you can use regular strings for Title and MessageFormat.
    internal static readonly LocalizableString Title = new LocalizableResourceString(nameof(Resources.AnalyzerTitle), Resources.ResourceManager, typeof(Resources));
    internal static readonly LocalizableString MessageFormat = new LocalizableResourceString(nameof(Resources.AnalyzerMessageFormat), Resources.ResourceManager, typeof(Resources));
    internal static readonly LocalizableString Description = new LocalizableResourceString(nameof(Resources.AnalyzerDescription), Resources.ResourceManager, typeof(Resources));
    internal const string Category = "Naming";

    internal static DiagnosticDescriptor Rule = new DiagnosticDescriptor(DiagnosticId, Title, MessageFormat, Category, DiagnosticSeverity.Warning, isEnabledByDefault: true, description: Description);

    public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get { return ImmutableArray.Create(Rule); } }
    
    ...
}