vb.net的最小值和最大值

Question

我正在创建一个程序，需要在Log_Type = I中过滤min log_time，在Log_Type = O中过滤最大logtime。需要在reportviewer中显示。谢谢你们，我不知道如何从最小和最大开始

Answer 1

所以，您使用DataSet DataSource作为ReportViewer从MySql - 数据库填充的DataSet。然后你应该首先过滤Linq-To-DataSet或者通过sql过滤。

例如（通过Dim groups = From row In ds.Tables(0) Let id = row.Field(Of Int32)("ID") Let empId = row.Field(Of String)("EMP_ID").Trim() Let logType = row.Field(Of String)("LOG_TYPE").Trim() Let logDate = row.Field(Of Date)("LOG_DATE") Let logTime = row.Field(Of TimeSpan)("LOG_TIME") Let creditDate = row.Field(Of Date)("CREDIT_DATE") Select data = New With {id, empId, logType, logDate, logTime, creditDate, row} Group data By data.empId, data.logType Into TypeGroup = Group Dim newDataSource As DataTable = ds.Tables(0).Clone() ' empty table with same schema ' For Each grp In groups Dim iGroup = From data In grp.TypeGroup Where StringComparer.OrdinalIgnoreCase.Equals("i", data.logType) Dim min = (From data In iGroup Order By data.logTime Ascending).FirstOrDefault() Dim max = (From data In iGroup Order By data.logTime Descending).FirstOrDefault() If min IsNot Nothing Then newDataSource.Rows.Add(min.id, min.empId, min.logType, min.logDate, min.logTime, min.creditDate) End If If max IsNot Nothing AndAlso Not Object.ReferenceEquals(min, max) Then newDataSource.Rows.Add(max.id, max.empId, max.logType, max.logDate, max.logTime, max.creditDate) End If Dim oGroup = From data In grp.TypeGroup Where StringComparer.OrdinalIgnoreCase.Equals("o", data.logType) min = (From data In oGroup Order By data.logTime Ascending).FirstOrDefault() max = (From data In oGroup Order By data.logTime Descending).FirstOrDefault() If min IsNot Nothing Then newDataSource.Rows.Add(min.id, min.empId, min.logType, min.logDate, min.logTime, min.creditDate) End If If max IsNot Nothing AndAlso Not Object.ReferenceEquals(min, max) Then newDataSource.Rows.Add(max.id, max.empId, max.logType, max.logDate, max.logTime, max.creditDate) End If Next ds.Tables.Clear() ds.Tables.Add(newDataSource) ）：

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