AppContext.cs

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using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Diagnostics.Tracing;
using System.IO;
using System.Reflection;
using System.Runtime.ExceptionServices;
using System.Runtime.Loader;
using System.Runtime.Versioning;
using System.Threading;
 
namespace System;
 
public static class AppContext
{
    private static Dictionary<string, object> s_dataStore;
 
    private static Dictionary<string, bool> s_switches;
 
    private static string s_defaultBaseDirectory;
 
    public static string BaseDirectory => (GetData("APP_CONTEXT_BASE_DIRECTORY") as string) ?? s_defaultBaseDirectory ?? (s_defaultBaseDirectory = GetBaseDirectoryCore());
 
    public static string? TargetFrameworkName => Assembly.GetEntryAssembly()?.GetCustomAttribute<TargetFrameworkAttribute>()?.FrameworkName;
 
    public static event UnhandledExceptionEventHandler? UnhandledException;
 
    public static event EventHandler<FirstChanceExceptionEventArgs>? FirstChanceException;
 
    public static event EventHandler? ProcessExit;
 
    public static object? GetData(string name)
    {
        if (name == null)
        {
            throw new ArgumentNullException("name");
        }
        if (s_dataStore == null)
        {
            return null;
        }
        lock (s_dataStore)
        {
            s_dataStore.TryGetValue(name, out var value);
            return value;
        }
    }
 
    public static void SetData(string name, object? data)
    {
        if (name == null)
        {
            throw new ArgumentNullException("name");
        }
        if (s_dataStore == null)
        {
            Interlocked.CompareExchange(ref s_dataStore, new Dictionary<string, object>(), null);
        }
        lock (s_dataStore)
        {
            s_dataStore[name] = data;
        }
    }
 
    internal static void OnProcessExit()
    {
        AssemblyLoadContext.OnProcessExit();
        if (EventSource.IsSupported)
        {
            EventListener.DisposeOnShutdown();
        }
        AppContext.ProcessExit?.Invoke(AppDomain.CurrentDomain, EventArgs.Empty);
    }
 
    public static bool TryGetSwitch(string switchName, out bool isEnabled)
    {
        if (switchName == null)
        {
            throw new ArgumentNullException("switchName");
        }
        if (switchName.Length == 0)
        {
            throw new ArgumentException(SR.Argument_EmptyName, "switchName");
        }
        if (s_switches != null)
        {
            lock (s_switches)
            {
                if (s_switches.TryGetValue(switchName, out isEnabled))
                {
                    return true;
                }
            }
        }
        if (GetData(switchName) is string value && bool.TryParse(value, out isEnabled))
        {
            return true;
        }
        isEnabled = false;
        return false;
    }
 
    public static void SetSwitch(string switchName, bool isEnabled)
    {
        if (switchName == null)
        {
            throw new ArgumentNullException("switchName");
        }
        if (switchName.Length == 0)
        {
            throw new ArgumentException(SR.Argument_EmptyName, "switchName");
        }
        if (s_switches == null)
        {
            Interlocked.CompareExchange(ref s_switches, new Dictionary<string, bool>(), null);
        }
        lock (s_switches)
        {
            s_switches[switchName] = isEnabled;
        }
    }
 
    internal unsafe static void Setup(char** pNames, char** pValues, int count)
    {
        s_dataStore = new Dictionary<string, object>(count);
        for (int i = 0; i < count; i++)
        {
            s_dataStore.Add(new string(pNames[i]), new string(pValues[i]));
        }
    }
 
    [UnconditionalSuppressMessage("SingleFile", "IL3000: Avoid accessing Assembly file path when publishing as a single file", Justification = "Single File apps should always set APP_CONTEXT_BASE_DIRECTORY therefore code handles Assembly.Location equals null")]
    private static string GetBaseDirectoryCore()
    {
        string path = Assembly.GetEntryAssembly()?.Location;
        string text = Path.GetDirectoryName(path);
        if (text == null)
        {
            return string.Empty;
        }
        if (!Path.EndsInDirectorySeparator(text))
        {
            text += "\\";
        }
        return text;
    }
 
    internal static void LogSwitchValues(RuntimeEventSource ev)
    {
        if (s_switches != null)
        {
            lock (s_switches)
            {
                foreach (KeyValuePair<string, bool> s_switch in s_switches)
                {
                    ev.LogAppContextSwitch(s_switch.Key, s_switch.Value ? 1 : 0);
                }
            }
        }
        if (s_dataStore == null)
        {
            return;
        }
        lock (s_dataStore)
        {
            if (s_switches != null)
            {
                lock (s_switches)
                {
                    LogDataStore(ev, s_switches);
                    return;
                }
            }
            LogDataStore(ev, null);
        }
        static void LogDataStore(RuntimeEventSource ev, Dictionary<string, bool> switches)
        {
            foreach (KeyValuePair<string, object> item in s_dataStore)
            {
                if (item.Value is string value && bool.TryParse(value, out var result) && (switches == null || !switches.ContainsKey(item.Key)))
                {
                    ev.LogAppContextSwitch(item.Key, result ? 1 : 0);
                }
            }
        }
    }
}