Enhance KeyedLock with additional locking methods and improve documentation

framework/src/Volo.Abp.Core/Volo/Abp/Threading/KeyedLock.cs

@@ -6,20 +6,58 @@ using System.Threading.Tasks;
 namespace Volo.Abp.Threading;
 
 /// <summary>
-/// Per-key asynchronous lock.
-/// https://stackoverflow.com/a/31194647
+/// Per-key asynchronous lock for coordinating concurrent flows.
 /// </summary>
+/// <remarks>
+/// Based on the pattern described in https://stackoverflow.com/a/31194647.
+/// Use within a <c>using</c> scope to ensure the lock is released via <c>IDisposable.Dispose()</c>.
+/// </remarks>
 public static class KeyedLock
 {
     private static readonly Dictionary<object, RefCounted<SemaphoreSlim>> SemaphoreSlims = new();
 
+    /// <summary>
+    /// Acquires an exclusive asynchronous lock for the specified <paramref name="key"/>.
+    /// This method waits until the lock becomes available.
+    /// </summary>
+    /// <param name="key">A non-null object that identifies the lock. Objects considered equal by dictionary semantics will share the same lock.</param>
+    /// <returns>An <see cref="IDisposable"/> handle that must be disposed to release the lock.</returns>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="key"/> is <see langword="null"/>.</exception>
+    /// <example>
+    /// <code>
+    /// var key = "my-critical-section";
+    /// using (await KeyedLock.LockAsync(key))
+    /// {
+    ///     // protected work
+    /// }
+    /// </code>
+    /// </example>
     public static async Task<IDisposable> LockAsync(object key)
     {
+        Check.NotNull(key, nameof(key));
         return await LockAsync(key, CancellationToken.None);
     }
 
+    /// <summary>
+    /// Acquires an exclusive asynchronous lock for the specified <paramref name="key"/>, observing a <paramref name="cancellationToken"/>.
+    /// </summary>
+    /// <param name="key">A non-null object that identifies the lock. Objects considered equal by dictionary semantics will share the same lock.</param>
+    /// <param name="cancellationToken">A token to cancel the wait for the lock.</param>
+    /// <returns>An <see cref="IDisposable"/> handle that must be disposed to release the lock.</returns>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="key"/> is <see langword="null"/>.</exception>
+    /// <exception cref="OperationCanceledException">Thrown if the wait is canceled via <paramref name="cancellationToken"/>.</exception>
+    /// <example>
+    /// <code>
+    /// var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5));
+    /// using (await KeyedLock.LockAsync("db-update", cts.Token))
+    /// {
+    ///     // protected work
+    /// }
+    /// </code>
+    /// </example>
     public static async Task<IDisposable> LockAsync(object key, CancellationToken cancellationToken)
     {
+        Check.NotNull(key, nameof(key));
         var semaphore = GetOrCreate(key);
         try
         {
@@ -34,13 +72,62 @@ public static class KeyedLock
         return new Releaser(key);
     }
 
+    /// <summary>
+    /// Attempts to acquire an exclusive lock for the specified <paramref name="key"/> without waiting.
+    /// </summary>
+    /// <param name="key">A non-null object that identifies the lock.</param>
+    /// <returns>
+    /// An <see cref="IDisposable"/> handle if the lock was immediately acquired; otherwise <see langword="null"/>.
+    /// </returns>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="key"/> is <see langword="null"/>.</exception>
+    /// <example>
+    /// <code>
+    /// var handle = await KeyedLock.TryLockAsync("cache-key");
+    /// if (handle != null)
+    /// {
+    ///     using (handle)
+    ///     {
+    ///         // protected work
+    ///     }
+    /// }
+    /// </code>
+    /// </example>
     public static async Task<IDisposable?> TryLockAsync(object key)
     {
+        Check.NotNull(key, nameof(key));
         return await TryLockAsync(key, default, CancellationToken.None);
     }
 
+    /// <summary>
+    /// Attempts to acquire an exclusive lock for the specified <paramref name="key"/>, waiting up to <paramref name="timeout"/>.
+    /// </summary>
+    /// <param name="key">A non-null object that identifies the lock.</param>
+    /// <param name="timeout">Maximum time to wait for the lock. If set to <see cref="TimeSpan.Zero"/>, the method performs an immediate, non-blocking attempt.</param>
+    /// <param name="cancellationToken">A token to cancel the wait.</param>
+    /// <returns>
+    /// An <see cref="IDisposable"/> handle if the lock was acquired within the timeout; otherwise <see langword="null"/>.
+    /// </returns>
+    /// <exception cref="ArgumentNullException">Thrown when <paramref name="key"/> is <see langword="null"/>.</exception>
+    /// <exception cref="OperationCanceledException">Thrown if the wait is canceled via <paramref name="cancellationToken"/>.</exception>
+    /// <example>
+    /// <code>
+    /// var handle = await KeyedLock.TryLockAsync("send-mail", TimeSpan.FromSeconds(1));
+    /// if (handle != null)
+    /// {
+    ///     using (handle)
+    ///     {
+    ///         // protected work
+    ///     }
+    /// }
+    /// else
+    /// {
+    ///     // lock not acquired within timeout
+    /// }
+    /// </code>
+    /// </example>
     public static async Task<IDisposable?> TryLockAsync(object key, TimeSpan timeout, CancellationToken cancellationToken = default)
     {
+        Check.NotNull(key, nameof(key));
         var semaphore = GetOrCreate(key);
         bool acquired;
         try