Help Solving: Does not contain a definition for 'Select'.....

Question

Hi,

Need help solving a Task that returns a Task<IEnumerable<Writing>> so I can fill ObservableCollection<ViewModels.IWritingItemViewModel> Writings for my Design Time Data Page:

<d:Page.DataContext>
	<designTimeData:MainPageViewModel />
</d:Page.DataContext>

My constructor does this:

public MainPageViewModel()
{
	var writings = this.GetGroupsAsync();
	this.Writings = new ObservableCollection<ViewModels.IWritingItemViewModel>();

	var viewmodels = writings.Select((x, i) => new WritingItemViewModel
	{
		Writing = x,
		VariableItemSize = (i == 0) ? Common.VariableItemSizes.Writings : Common.VariableItemSizes.Normal,
	});
}

My var writings = this.GetGroupsAsync(); is:

public async Task<IEnumerable<Writing>> GetGroupsAsync()
{
	await this.GetMenuDataAsync();

	return this.Groups;
}

which in turn gets data from:

private async Task GetMenuDataAsync()
{
	Uri dataUri = new Uri("ms-appx:///DesignTimeData/MenuData.json");

	StorageFile file = await StorageFile.GetFileFromApplicationUriAsync(dataUri);
	string jsonText = await FileIO.ReadTextAsync(file);
	JsonObject jsonObject = JsonObject.Parse(jsonText);
	JsonArray jsonArray = jsonObject["Groups"].GetArray();

	foreach (JsonValue groupValue in jsonArray)
	{
		JsonObject groupObject = groupValue.GetObject();
		Writing group = new Writing(
			groupObject["UniqueId"].GetString(),
			groupObject["IsHeaderInteractive"].GetBoolean(),
			groupObject["ViewType"].GetString(),
			groupObject["ModelType"].GetString(),
			groupObject["Page"].GetString(),
			groupObject["Title"].GetString(),
			groupObject["Subtitle"].GetString(),
			groupObject["ImagePath"].GetString(),
			groupObject["Description"].GetString(),
			groupObject["GroupId"].GetString()
			);

		foreach (JsonValue itemValue in groupObject["WritingMenus"].GetArray())
		{
			JsonObject itemObject = itemValue.GetObject();
			group.WritingMenus.Add(new WritingMenu(
				itemObject["UniqueId"].GetString(),
				itemObject["Page"].GetString(),
				itemObject["Title"].GetString(),
				itemObject["Subtitle"].GetString(),
				itemObject["ImagePath"].GetString(),
				itemObject["Description"].GetString(),
				itemObject["Content"].GetString(),
				itemObject["WritingsId"].GetString(),
				itemObject["GroupId"].GetString(),
				Convert.ToInt32(itemObject["Item"].ValueType)
				));
		}
		this.Groups.Add(group);
	}
}

and I get this Error:

Error 5 'System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<App1.DesignTimeData.Writing>>' 
  does not contain a definition for 'Select' and no extension method 'Select' accepting a first argument of type 
  'System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<App1.DesignTimeData.Writing>>' 
  could be found (are you missing a using directive or an assembly reference?)

I'm creating collections of:

public interface IWritingItemViewModel : Common.IVariableSizedItem
{
	Models.Writing Writing { get; set; }
}

and my class for creating data is:

public class Writing
{
	public Writing(
	string uniqueId,
	bool isHeaderInteractive,
	string templateType,
	string viewModelType,
	string page,
	string title,
	string subtitle,
	string imagePath,
	string description,
	string groupId
		)
	{
		this.UniqueId = uniqueId;
		this.IsHeaderInteractive = isHeaderInteractive;
		this.TemplateType = templateType;
		this.ViewModelType = viewModelType;
		this.Page = page;
		this.Title = title;
		this.Subtitle = subtitle;
		this.ImagePath = imagePath;
		this.Description = description;
		this.GroupId = groupId;
		this.WritingMenus = new ObservableCollection<WritingMenu>();
	}

	public string UniqueId { get; private set; }
	public bool IsHeaderInteractive { get; private set; }
	public string TemplateType { get; private set; }
	public string ViewModelType { get; private set; }
	public string Page { get; private set; }
	public string Title { get; private set; }
	public string Subtitle { get; private set; }
	public string ImagePath { get; private set; }
	public string Description { get; private set; }
	public string GroupId { get; private set; }

	public virtual ObservableCollection<WritingMenu> WritingMenus { get; private set; }
}

How can I solve or successfully complete this code?

Thanks!...

---

Code is like a box of chocolates!...

Answer 1

Hi VcDeveloper,

The first error looks like the Linq you are using is not correct.

Did you have referenced to "using System.Linq;" in your code?

--James

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Answer 2

Hi James,

Yes I have and for now I had to hand code the sample data which; I wanted to avoid by trying to read a .json file, but I couldn't get the async Task to work.

---

Code is like a box of chocolates!...

Answer 3

I looked into your error message again, I found something interesting:

Error 5 'System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<App1.DesignTimeData.Writing>>'
  does not contain a definition for 'Select' and no extension method 'Select' accepting a first argument of type
  'System.Threading.Tasks.Task<System.Collections.Generic.IEnumerable<App1.DesignTimeData.Writing>>'
  could be found (are you missing a using directive or an assembly reference?)

That means: Task does not contain the definition for Select. This was reasonable, Task does not inherit IEnumerable interface.

	var viewmodels = writings.Select((x, i) => new WritingItemViewModel
	{
		Writing = x,
		VariableItemSize = (i == 0) ? Common.VariableItemSizes.Writings : Common.VariableItemSizes.Normal,
	});

        public async Task<IEnumerable<Writing>> GetGroupsAsync()

You need get the IEnumerable<Writing> for Select use. See this for more information: How to: Return a Value from a Task

--James

---

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