如果不得不猜测,与使用sqldataadapter和fill()方法相比,使用sqldatareader填充数据表没有任何性能优势。
唯一真正验证理论的方法是编写自己的实现并进行比较。但您也可以查看fill()正在执行的代码,以查看它到底在做什么。我建议下载
Reflector
看看代码。
我自己做的。下面是在调用fill()之后最终调用的内容:
Protected Overridable Function Fill(ByVal dataTables As DataTable(), ByVal dataReader As IDataReader, ByVal startRecord As Integer, ByVal maxRecords As Integer) As Integer
Dim num3 As Integer
Dim ptr As IntPtr
Bid.ScopeEnter(ptr, "<comm.DataAdapter.Fill|API> %d#, dataTables[], dataReader, startRecord, maxRecords" & ChrW(10), Me.ObjectID)
Try
ADP.CheckArgumentLength(dataTables, "tables")
If (((dataTables Is Nothing) OrElse (dataTables.Length = 0)) OrElse (dataTables(0) Is Nothing)) Then
Throw ADP.FillRequires("dataTable")
End If
If (dataReader Is Nothing) Then
Throw ADP.FillRequires("dataReader")
End If
If ((1 < dataTables.Length) AndAlso ((startRecord <> 0) OrElse (maxRecords <> 0))) Then
Throw ADP.NotSupported
End If
Dim num2 As Integer = 0
Dim enforceConstraints As Boolean = False
Dim dataSet As DataSet = dataTables(0).DataSet
Try
If (Not dataSet Is Nothing) Then
enforceConstraints = dataSet.EnforceConstraints
dataSet.EnforceConstraints = False
End If
Dim i As Integer
For i = 0 To dataTables.Length - 1
If dataReader.IsClosed Then
goto Label_00DE
End If
Dim container As DataReaderContainer = DataReaderContainer.Create(dataReader, Me.ReturnProviderSpecificTypes)
If (container.FieldCount > 0) Then
If ((0 < i) AndAlso Not Me.FillNextResult(container)) Then
goto Label_00DE
End If
Dim num4 As Integer = Me.FillFromReader(Nothing, dataTables(i), Nothing, container, startRecord, maxRecords, Nothing, Nothing)
If (i = 0) Then
num2 = num4
End If
End If
Next i
Catch exception1 As ConstraintException
enforceConstraints = False
Throw
Finally
If enforceConstraints Then
dataSet.EnforceConstraints = True
End If
End Try
Label_00DE:
num3 = num2
Finally
Bid.ScopeLeave((ptr))
End Try
Return num3
End Function
您会注意到这会调用FillFromReader():
Friend Function FillFromReader(ByVal dataset As DataSet, ByVal datatable As DataTable, ByVal srcTable As String, ByVal dataReader As DataReaderContainer, ByVal startRecord As Integer, ByVal maxRecords As Integer, ByVal parentChapterColumn As DataColumn, ByVal parentChapterValue As Object) As Integer
Dim num2 As Integer = 0
Dim schemaCount As Integer = 0
Do
If (0 < dataReader.FieldCount) Then
Dim mapping As SchemaMapping = Me.FillMapping(dataset, datatable, srcTable, dataReader, schemaCount, parentChapterColumn, parentChapterValue)
schemaCount += 1
If (((Not mapping Is Nothing) AndAlso (Not mapping.DataValues Is Nothing)) AndAlso (Not mapping.DataTable Is Nothing)) Then
mapping.DataTable.BeginLoadData
Try
If ((1 = schemaCount) AndAlso ((0 < startRecord) OrElse (0 < maxRecords))) Then
num2 = Me.FillLoadDataRowChunk(mapping, startRecord, maxRecords)
Else
Dim num3 As Integer = Me.FillLoadDataRow(mapping)
If (1 = schemaCount) Then
num2 = num3
End If
End If
Finally
mapping.DataTable.EndLoadData
End Try
If (Not datatable Is Nothing) Then
Return num2
End If
End If
End If
Loop While Me.FillNextResult(dataReader)
Return num2
End Function
在看了所有这些之后,我可能不得不改变主意。为所有这些编写自己的实现可能确实有一个可衡量的改进。这些函数中的逻辑比我预期的要多,并且在一遍又一遍地调用FillNextResult()时也会有一些函数调用开销。
