Linq将两个语句合并为一个大语句（优化）

Question

我有一种方法，它使用大量LINQ来设置和匹配Tuple<string, int>列表中的某些值。

现在我仍然坚持嵌套到eachother中的两个foreach循环，我认为它可以将它们组合成一个巨大的LINQ查询。我想知道如何将优化作为一个大的条件来做到这一点，最好的办法是什么。

这是我讲的功能：

private async void AddLocalChangesFromPendingOperations() 
{ 
    var pendingOperations = await this.operationsStorage.GetOperationsAsync(); 
    var list = pendingOperations. 
     SelectMany(pendingOperation => 
          pendingOperation.Settings, (pendingOperation, setting) => 
          new { pendingOperation, setting }) 
     .Where(a => a.setting.Key == "selection") 
     .Select(a => new Tuple<string, int>(
              a.pendingOperation.DefinitionId, 
              Convert.ToInt32(a.setting.Value.ValueObject))) 
     .ToList(); 

    foreach (var pendingChange in list) 
    { 
     var selection = await this.selectionsStorage.GetSelectionByIdAsync(pendingChange.Item2); 
     foreach (var selectionsViewModel in this.SelectionsList.Where(a => a.Name == selection.Name)) 
     { 
      if (pendingChange.Item1 == "selection-add-animals") 
      { 
       selectionsViewModel.IsActive = true; 
      } 
      else if (pendingChange.Item1 == "selection-remove-animals") 
      { 
       selectionsViewModel.IsActive = false; 
      } 
     } 
    } 
} 

如果可能的话，我想同时使用LINQ优化最后两个foreaches。我试过的东西，但我被困在当前列表的设置值...

我这样做：

this.SelectionsList = this 
    .SelectionsList 
    .Where(a => a.Name == selection.Name) 
    .SingleOrDefault(
     a => pendingChange.Item1 == "selection-add-animals" ? a.IsActive = true : a.IsActive = false 
    ); 

Answer 1

在一般来说，LINQ用于查询项目（Language Integrated Query）。然而，你可以做一个查询，然后在最后做一个foreach：

private async void AddLocalChangesFromPendingOperations() 
{ 
    var pendingOperations = await this.operationsStorage.GetOperationsAsync(); 

    (await Task.WhenAll(pendingOperations 
     .SelectMany(pendingOperation => 
          pendingOperation.Settings, (pendingOperation, setting) => 
          new { pendingOperation, setting }) 
     .Where(a => a.setting.Key == "selection") 
     .Select(a => Tuple.Create(a.pendingOperation.DefinitionId, Convert.ToInt32(a.setting.Value.ValueObject))) 
     .Select(async pendingChange => Tuple.Create(await this.selectionsStorage.GetSelectionByIdAsync(pendingChange.Item2)), pendingChange)) 
     .SelectMany(tuple => this.SelectionsList.Where(a => a.Name == tuple.Item1.Name) 
               .Select(selectionsViewModel => Tuple.Create(selectionsViewModel, tuple.Item2)) 
     .Select(tuple => Tuple.Create(tuple.Item1, tuple.Item2.Item1 == "selection-add-animals")) 
     .ToList() 
     .ForEach(tuple => tuple.Item1.IsActive = tuple.Item2); 
} 

这是否是更清晰的比你原来的实施问题讨论（我不认为这是），但它是一种方法做到这一点。

注意：这是直接键入编辑器，可能会有一些小的语法错误。

Answer 2

你可以这样做：

this.SelectionsList = this.SelectionsList 
    .Where(a => a.Name == selection.Name) 
    .Select(a => 
    { 
     a.IsActive = a.Name == selection.Name ? true:false; 
     return a; 
    }).ToList();