Linq 查询以列出 VB.NET
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Linq query to list VB.NET
提问by serhio
Dim query = From o In myContainer.MyObjects Select o.MyStringProperty Distinct
Dim myProperties As List(Of String) = query.ToList????? 'no way!!!'
"query" type is IEnumerable(Of String)
“查询”类型是 IEnumerable(Of String)
I tried to use the querydirectly as a DataSource of a (infragistic) combobox, but it throws me NullReferenceException, so I decided to convert it to a listof strings, to be a more "classical" datasource.
我尝试将query直接用作（infragistic）组合框的数据源，但它向我抛出 NullReferenceException，因此我决定将其转换为字符串列表，以成为更“经典”的数据源。
Dim values As List(Of String) = query.AsQueryable().ToList()
does not work either: Value of type 'System.Collections.Generic.List(Of System.Linq.IQueryable(Of String))' cannot be converted to 'System.Collections.Generic.List(Of String)'.
也不起作用：“System.Collections.Generic.List(Of System.Linq.IQueryable(Of String))”类型的值不能转换为“System.Collections.Generic.List(Of String)”。
采纳答案by serhio
Finally, solved with good old method : )
最后，用很好的旧方法解决了:)
Dim values As New List(Of String)
For Each item In query
values.Add(item)
Next item
回答by Reed Copsey
Your error message suggests the queryis actually a List(Of T)containing a collection internally.
您的错误消息表明query它实际上是一个List(Of T)包含内部集合的集合。
If this is the case, you can use SelectManyto flatten the collection:
如果是这种情况，您可以使用SelectMany扁平化集合：
Dim values As List(Of String) = query.SelectMany(Function(m) m).ToList()
Edit: Given your edit, as well as the comment, the following should work fine:
编辑：鉴于您的编辑以及评论，以下内容应该可以正常工作：
Dim values As List(Of String) = query.ToList()
回答by avanek
Perhaps you should try to specify the type on the query variable?
也许您应该尝试在查询变量上指定类型？
Dim query = From o In myContainer.MyObjects Select o.MyStringProperty Distinct
Should become
应该成为
Dim query As IEnumerable(Of String) = From o In myContainer.MyObjects Select o.MyStringProperty Distinct
If the type of IEnumerable(Of String) can't be used on query, then you need to flatten the list as Reed Copsey said.
如果 IEnumerable(Of String) 的类型不能用于查询，那么您需要像 Reed Copsey 所说的那样展平列表。
