Question

我的LINQ查询：

Dim groupedData = (From p In pData _
                   Group By p.TruncParam Into Group) _
                  .SelectMany(Function(g) g.Group) _
                  .Select(Function(d, idx) New With { _
                      .NewParameter = String.Concat(If(d.TruncParam.Length < 5, d.TruncParam, d.TruncParam.Substring(0, 5)), idx.ToString("0000")), _
                      .FullParameter = String.Format("{0}-{1} [{2}] <{3}>", d.LabName, d.TestName, d.Parameter, d.Unit)})

产生以下结果：

ID: SOLUB0000  Name: 001-AMT SOLUBL  [SOLUBLES]       <%>
ID: SOLUB0001  Name: CHEM-C4:SOL     [SOLUBLES]       <%>
ID: SOLUB0002  Name: CHEM-EMCARB:SOL [SOLUBLES]       <%>
ID: INSOL0003  Name: 001-AMT:INSOL   [INSOLUBLES]     <%>
ID: INSOL0004  Name: CHEM-AMT:INSOL  [INSOLUBLES]     <%>
ID: INSOL0005  Name: CHEM-W:INSOL    [INSOLUBLES]     <%>
ID: INSOL0006  Name: CHEM-W:INSOL    [INSOLUBLES]     <mg/l>
ID: CLRES0007  Name: 001-CL RESIDUE  [CL RESIDUE]     <ppm>
ID: SUMCA0008  Name: 001-ELEMENTS    [SUM CA K NA SI] <%>
ID: SUMME0009  Name: 001-ELEMENTS    [SUM METALS + P] <%>

当TruncParam更改时，我希望idx子句中的索引（Select）重置为1.因此，在上面的列表中，索引应为{{ 1}}，SOLUB0001，SOLUB0002，INSOL0001 ... INSOL0002，CLRES0001，SUMCA0001。

我应该如何改变LINQ查询？

Answer 1

您需要在SelectMany语句（g.Group.Select(d, idx) => new {d, idx}）中移动索引选择，如下所示：

Dim groupedData = (From p In pData _
                   Group By p.TruncParam Into Group) _
    .SelectMany(Function(g) g.Group.Select(Function(d, idx) New With { _
        .Element = d, .Index = idx}) _
    .Select(Function(d) New With { _
        .NewParameter = String.Concat(If(d.Element.TruncParam.Length < 5, d.Element.TruncParam, d.Element.TruncParam.Substring(0, 5)), d.Index.ToString("0000")), _
        .FullParameter = String.Format("{0}-{1} [{2}] <{3}>", d.Element.LabName, d.Element.TestName, d.Element.Parameter, d.Element.Unit)})

在LINQ Select子句中重置索引

1 个答案: