在 vb.net 中将查询结果转换为字典
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convert query result to dictionary in vb.net
提问by dinotom
What is the proper syntax for .ToDictionary to return the following as a Dictionary(Of String, String) where ShortDesc is the key and CurrentFrontSymbol is the value
.ToDictionary 将以下内容作为 Dictionary(Of String, String) 返回的正确语法是什么，其中 ShortDesc 是键，CurrentFrontSymbol 是值
Dim dicQuery As Dictionary(Of String, String) = (From d In toolkitEntities.currentfrontcommoditysymbols
Select d.ShortDesc, d.CurrentFrontSymbol)
Update
更新
And can the following functions query and following For Each loop become one LINQ query?
并且以下函数可以查询和跟随 For Each 循环成为一个 LINQ 查询吗？
Public Shared Function GetRangeProjectionPerformance(Optional daysToRetrieve As Integer = 100) As Dictionary(Of Integer, List(Of ProjectionPerformance))
Dim todaysDate As Date = DateTime.Now.Date
Dim lookbackDate As Date = todaysDate.AddDays(daysToRetrieve * -1)
Dim temp As New Dictionary(Of Integer, List(Of ProjectionPerformance))
Using ctx As New ProjectionsEntities()
Dim query = (From d In ctx.projections
Where d.SymbolId <= 42 AndAlso d.Date >= lookbackDate
Join t In ctx.symbols On d.SymbolId Equals t.Id
Let actualRange = d.HighProjection - d.LowProjection
Select New With {
d.Date,
d.SymbolId,
t.Name,
actualRange}).GroupBy(Function(o) o.SymbolId).ToDictionary(Function(p) p.Key)
For Each itm In query
Dim rpp As New ProjectionPerformance
Dim rppList As New List(Of ProjectionPerformance)
If itm.Value.Count > 0 Then
For x As Integer = 0 To itm.Value.Count - 1
Dim bb As Integer = Convert.ToInt32(itm.Value(x).SymbolId)
With rpp
.SymbolId = bb
.ProjectionDate = itm.Value(x).Date.ToString()
.Name = itm.Value(x).Name
.ProjectedRange = itm.Value(x).actualRange
End With
rppList.Add(rpp)
Next
End If
temp.Add(itm.Key, rppList)
Next
End Using
Return temp
End Function
回答by Markus
As you do not have a special projection in the select, you can just call ToDictionaryon the collection. The first lambda expression retrieves the key, the second one the value.
由于您在选择中没有特殊投影，您可以调用ToDictionary集合。第一个 lambda 表达式检索键，第二个表达式检索值。
Dim dicQuery = toolkitEntities.currentfrontcommoditysymbols.ToDictionary( _
Function(x) x.ShortDesc, _
Function(y) y.CurrentFrontSymbol)
As for your update: the following query should get you the desired result:
至于您的更新：以下查询应该会得到您想要的结果：
Dim query = (From d In ctx.projections
Where d.SymbolId <= 42 AndAlso d.Date >= lookbackDate
Join t In ctx.symbols On d.SymbolId Equals t.Id
Let actualRange = d.HighProjection - d.LowProjection
Select New With {
d.Date,
d.SymbolId,
t.Name,
actualRange}).GroupBy(Function(o) o.SymbolId)
.ToDictionary(Function(p) p.Key,
Function(x) x.Select(Function(y) New ProjectionPerformance() With {
.SymbolId = Convert.ToInt32(y.SymbolId),
.ProjectionDate = y.Date.ToString(),
.Name = y.Name,
.ProjectedRange = y.actualRange
}).ToList())
