added similar helpers for assistants

README.md

@@ -484,13 +484,7 @@ Next, create a new thread. For illustrative purposes, you could include an initi
 ```csharp
 ThreadCreationOptions threadOptions = new()
 {
-    InitialMessages =
-    {
-        new ThreadInitializationMessage(new List<MessageContent>()
-        {
-            MessageContent.FromText("How well did product 113045 sell in February? Graph its trend over time."),
-        }),
-    },  
+    InitialMessages = { "How well did product 113045 sell in February? Graph its trend over time." }
 };
 
 ThreadRun threadRun = assistantClient.CreateThreadAndRun(assistant.Id, threadOptions);

examples/Assistants/Example01_RetrievalAugmentedGeneration.cs

@@ -85,13 +85,7 @@ public void Example01_RetrievalAugmentedGeneration()
         // Now we'll create a thread with a user query about the data already associated with the assistant, then run it
         ThreadCreationOptions threadOptions = new()
         {
-            InitialMessages =
-            {
-                new ThreadInitializationMessage(new List<MessageContent>()
-                {
-                    MessageContent.FromText("How well did product 113045 sell in February? Graph its trend over time."),
-                }),
-            },
+            InitialMessages = { "How well did product 113045 sell in February? Graph its trend over time." }
         };
 
         ThreadRun threadRun = assistantClient.CreateThreadAndRun(assistant.Id, threadOptions);

examples/Assistants/Example02_FunctionCalling.cs

@@ -82,7 +82,7 @@ string GetCurrentWeather(string location, string unit = "celsius")
         // Create a thread with an initial user message and run it.
         ThreadCreationOptions threadOptions = new()
         {
-            InitialMessages = { new ThreadInitializationMessage(["What's the weather like today?"]), },
+            InitialMessages = { "What's the weather like today?" }
         };
 
         ThreadRun run = client.CreateThreadAndRun(assistant.Id, threadOptions);

examples/Assistants/Example02_FunctionCallingAsync.cs

@@ -82,7 +82,7 @@ string GetCurrentWeather(string location, string unit = "celsius")
         // Create a thread with an initial user message and run it.
         ThreadCreationOptions threadOptions = new()
         {
-            InitialMessages = { new ThreadInitializationMessage(["What's the weather like today?"]), },
+            InitialMessages = { "What's the weather like today?" }
         };
 
         ThreadRun run = await client.CreateThreadAndRunAsync(assistant.Id, threadOptions);

examples/Assistants/Example04_AllTheTools.cs

@@ -83,13 +83,10 @@ static string GetNameOfFamilyMember(string relation)
         {
             InitialMessages =
             {
-                new ThreadInitializationMessage(
-                    [
-                        "Create a graph of a line with a slope that's my father's favorite number "
-                        + "and an offset that's my mother's favorite number.",
-                        "Include people's names in your response and cite where you found them."
-                    ]),
-            },
+                "Create a graph of a line with a slope that's my father's favorite number "
+                + "and an offset that's my mother's favorite number.",
+                "Include people's names in your response and cite where you found them."
+            }
         });
 
         ThreadRun run = client.CreateRun(thread, assistant);

src/Custom/Assistants/ThreadInitializationMessage.cs

@@ -16,4 +16,15 @@ public ThreadInitializationMessage(IEnumerable<MessageContent> content) : base(c
     internal ThreadInitializationMessage(MessageCreationOptions baseOptions)
         : base(baseOptions.Role, baseOptions.Content, baseOptions.Attachments, baseOptions.Metadata, null)
     { }
+
+    /// <summary>
+    /// Implicitly creates a new instance of <see cref="ThreadInitializationMessage"/> from a single item of plain text
+    /// content.
+    /// </summary>
+    /// <remarks>
+    /// Using a <see cref="string"/> in the position of a <see cref="ThreadInitializationMessage"/> is equivalent to
+    /// using the <see cref="ThreadInitializationMessage(IEnumerable{MessageContent})"/> constructor with a single
+    /// <see cref="MessageContent.FromText(string)"/> content instance.
+    /// </remarks>
+    public static implicit operator ThreadInitializationMessage(string initializationMessage) => new([initializationMessage]);
 }

src/Custom/Chat/ChatMessageContentPart.cs

@@ -130,4 +130,14 @@ public static ChatMessageContentPart CreateImageMessageContentPart(BinaryData im
     /// </summary>
     /// <returns></returns>
     public override string ToString() => Text;
+
+    /// <summary>
+    /// Implicitly creates a new <see cref="ChatMessageContentPart"/> instance from an item of plain text.
+    /// </summary>
+    /// <remarks>
+    /// Using a <see cref="string"/> in the position of a <see cref="ChatMessageContentPart"/> is equivalent to
+    /// calling the <see cref="CreateTextMessageContentPart(string)"/> method.
+    /// </remarks>
+    /// <param name="content"> The text content to use as this content part. </param>
+    public static implicit operator ChatMessageContentPart(string content) => new(content);
 }