Add TryAdd to DependencyMaps

src/Discord.Net.Commands/Dependencies/DependencyMap.cs

@@ -18,12 +18,21 @@ namespace Discord.Commands
         public void Add<T>(T obj) where T : class 
             => AddFactory(() => obj);
         /// <inheritdoc />
+        public bool TryAdd<T>(T obj) where T : class
+            => TryAddFactory(() => obj);
+        /// <inheritdoc />
         public void AddTransient<T>() where T : class, new() 
             => AddFactory(() => new T());
         /// <inheritdoc />
+        public bool TryAddTransient<T>() where T : class, new()
+            => TryAddFactory(() => new T());
+        /// <inheritdoc />
         public void AddTransient<TKey, TImpl>() where TKey : class 
             where TImpl : class, TKey, new() 
             => AddFactory<TKey>(() => new TImpl());
+        public bool TryAddTransient<TKey, TImpl>() where TKey : class
+            where TImpl : class, TKey, new()
+            => TryAddFactory<TKey>(() => new TImpl());
         
         /// <inheritdoc />
         public void AddFactory<T>(Func<T> factory) where T : class
@@ -33,6 +42,15 @@ namespace Discord.Commands
                 throw new InvalidOperationException($"The dependency map already contains \"{t.FullName}\"");
             map.Add(t, factory);
         }
+        /// <inheritdoc />
+        public bool TryAddFactory<T>(Func<T> factory) where T : class
+        {
+            var t = typeof(T);
+            if (map.ContainsKey(t))
+                return false;
+            map.Add(t, factory);
+            return true;
+        }
 
         /// <inheritdoc />
         public T Get<T>()

src/Discord.Net.Commands/Dependencies/IDependencyMap.cs

@@ -11,11 +11,24 @@ namespace Discord.Commands
         /// <param name="obj">The instance of a service.</param>
         void Add<T>(T obj) where T : class;
         /// <summary>
+        /// Tries to add an instance of a service to be injected.
+        /// </summary>
+        /// <typeparam name="T">The type of service.</typeparam>
+        /// <param name="obj">The instance of a service.</param>
+        /// <returns>A bool, indicating if the service was successfully added to the DependencyMap.</returns>
+        bool TryAdd<T>(T obj) where T : class;
+        /// <summary>
         /// Add a service that will be injected by a new instance every time.
         /// </summary>
         /// <typeparam name="T">The type of instance to inject.</typeparam>
         void AddTransient<T>() where T : class, new();
         /// <summary>
+        /// Tries to add a service that will be injected by a new instance every time.
+        /// </summary>
+        /// <typeparam name="T">The type of instance to inject.</typeparam>
+        /// <returns>A bool, indicating if the service was successfully added to the DependencyMap.</returns>
+        bool TryAddTransient<T>() where T : class, new();
+        /// <summary>
         /// Add a service that will be injected by a new instance every time.
         /// </summary>
         /// <typeparam name="TKey">The type to look for when injecting.</typeparam>
@@ -25,11 +38,25 @@ namespace Discord.Commands
         /// </example>
         void AddTransient<TKey, TImpl>() where TKey: class where TImpl : class, TKey, new();
         /// <summary>
+        /// Tries to add a service that will be injected by a new instance every time.
+        /// </summary>
+        /// <typeparam name="TKey">The type to look for when injecting.</typeparam>
+        /// <typeparam name="TImpl">The type to inject when injecting.</typeparam>
+        /// <returns>A bool, indicating if the service was successfully added to the DependencyMap.</returns>
+        bool TryAddTransient<TKey, TImpl>() where TKey : class where TImpl : class, TKey, new();
+        /// <summary>
         /// Add a service that will be injected by a factory.
         /// </summary>
         /// <typeparam name="T">The type to look for when injecting.</typeparam>
         /// <param name="factory">The factory that returns a type of this service.</param>
         void AddFactory<T>(Func<T> factory) where T : class;
+        /// <summary>
+        /// Tries to add a service that will be injected by a factory.
+        /// </summary>
+        /// <typeparam name="T">The type to look for when injecting.</typeparam>
+        /// <param name="factory">The factory that returns a type of this service.</param>
+        /// <returns>A bool, indicating if the service was successfully added to the DependencyMap.</returns>
+        bool TryAddFactory<T>(Func<T> factory) where T : class;
 
         /// <summary>
         /// Pull an object from the map.