Poll

public class UpdateInputSample
{
    public async Task<Input> UpdateInputAsync(
         string projectId, string locationId, string inputId)
    {
        // Create the client.
        LivestreamServiceClient client = LivestreamServiceClient.Create();

        UpdateInputRequest request = new UpdateInputRequest
        {
            Input = new Input
            {
                InputName = InputName.FromProjectLocationInput(projectId, locationId, inputId),
                PreprocessingConfig = new PreprocessingConfig
                {
                    Crop = new PreprocessingConfig.Types.Crop
                    {
                        TopPixels = 5,
                        BottomPixels = 5
                    }
                }
            },
            UpdateMask = new FieldMask { Paths = { "preprocessing_config" } }
        };

        // Make the request.
        Operation<Input, OperationMetadata> response = await client.UpdateInputAsync(request);

        // Poll until the returned long-running operation is complete.
        Operation<Input, OperationMetadata> completedResponse = await response.PollUntilCompletedAsync();

        // Retrieve the operation result.
        return completedResponse.Result;
    }
}