Add documentation for synchronous access to asynchronous operations

docs/csharp/asynchronous-programming/async-scenarios.md

@@ -188,6 +188,71 @@ Avoid writing code that depends on the state of global objects or the execution
 
 A recommended goal is to achieve complete or near-complete [Referential Transparency](https://en.wikipedia.org/wiki/Referential_transparency) in your code. This approach results in a predictable, testable, and maintainable codebase.
 
+### Synchronous access to asynchronous operations
+
+In rare scenarios, you might need to block on asynchronous operations when the `await` keyword isn't available throughout your call stack. This situation commonly occurs in legacy codebases or when integrating asynchronous methods into synchronous APIs that can't be changed.
+
+> [!WARNING]
+> Synchronous blocking on asynchronous operations can lead to deadlocks and should be avoided whenever possible. The preferred solution is to use `async`/`await` throughout your call stack.
+
+When you must block synchronously on a `Task`, here are the available approaches, listed from most to least preferred:
+
+#### Use GetAwaiter().GetResult()
+
+The `GetAwaiter().GetResult()` pattern is generally the preferred approach when you must block synchronously:
+
+```csharp
+// When you cannot use await
+Task<string> task = GetDataAsync();
+string result = task.GetAwaiter().GetResult();
+```
+
+This approach:
+
+- Preserves the original exception without wrapping it in an `AggregateException`
+- Blocks the current thread until the task completes
+- Still carries deadlock risk if not used carefully
+
+#### Use Task.Run for complex scenarios
+
+For complex scenarios where you need to isolate the asynchronous work:
+
+```csharp
+// Offload to thread pool to avoid context deadlocks
+string result = Task.Run(async () => await GetDataAsync()).GetAwaiter().GetResult();
+```
+
+This pattern:
+
+- Executes the asynchronous method on a thread pool thread
+- Can help avoid some deadlock scenarios
+- Adds overhead by scheduling work to the thread pool
+
+#### Avoid Wait() and Result
+
+These blocking approaches are discouraged:
+
+```csharp
+// Discouraged: Wraps exceptions in AggregateException
+Task<string> task = GetDataAsync();
+task.Wait();
+string result = task.Result;
+```
+
+Problems with `Wait()` and `Result`:
+
+- Exceptions are wrapped in `AggregateException`, making error handling more complex
+- Higher deadlock risk
+- Less clear intent in code
+
+#### Additional considerations
+
+- **Deadlock prevention**: Be especially careful in UI applications or when using a synchronization context
+- **Performance impact**: Blocking threads reduces scalability
+- **Exception handling**: Test error scenarios carefully as exception behavior differs between patterns
+
+For more detailed guidance on the challenges and considerations of synchronous wrappers for asynchronous methods, see [Should I expose synchronous wrappers for asynchronous methods?](https://devblogs.microsoft.com/pfxteam/should-i-expose-synchronous-wrappers-for-asynchronous-methods/).
+
 ## Review the complete example
 
 The following code represents the complete example, which is available in the *Program.cs* example file.