Before C# 8, if you want to iterate over a collection, the data for that collection needs to be ready before iteration.
Basically, something like this was not possible prior to C# 8.
private static async IEnumerable<string> GetDataAsync()
{
for (var i = 0; i < 10; i++)
{
yield return await GetDataAsync(i);
}
}
What you can do is something like below.
private static IEnumerable<string> GetDataAsync()
{
for (var i = 0; i < 10; i++)
{
yield return GetDataAsync(i).Result;
}
}
But this will cause a thread block. With C# 8 comes the IAsyncEnumerable<T> which makes the yield return asynchronous.
private static async IAsyncEnumerable<string> GetDataAsync()
{
for (var i = 0; i < 10; i++)
{
yield return await GetDataAsync(i);
}
}
You can see that even though it’s an async method, it’s not returning a Task anymore. You can iterate over an IAsyncEnumerable<T> using await foreach making it an async stream.
await foreach (var item in GetDataAsync())
{
Console.WriteLine(item);
}
Isn’t it nice.
Happy Coding.
Regards,
Jaliya
