AO中保存二进制大对象(BLOB)-----将图层保存到数据库中

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本文提供了一个使用AO在数据库中保存和读取.lyr文件的示例代码。通过IMxDocument获取地图图层，并利用IPersistStream接口将图层保存为内存BLOB流，最后将BLOB流存入Access数据库。

AO中保存二进制大对象(BLOB)

示例代码演示如何保存一个.lyr文件

//保存
Private Sub UIButtonControl1_Click()
' Get the IPersistStream for the first layer from the map
Dim pMxDoc As IMxDocument
Set pMxDoc = ThisDocument

Dim pPersist As IPersistStream
Set pPersist = pMxDoc.FocusMap.Layer(0)

' Now persist the layer to the memory BLOB stream
Dim pMemoryStream As IMemoryBlobStream
Set pMemoryStream = New MemoryBlobStream

pPersist.Save pMemoryStream, False

' Finally, save the BLOB into the database
Dim pWorkspaceFactory As IWorkspaceFactory
Set pWorkspaceFactory = New AccessWorkspaceFactory

Dim pFeatureWorkspace As IFeatureWorkspace
Set pFeatureWorkspace =
pWorkspaceFactory.OpenFromFile("C:/Source/BLOB.mdb", 0)

Dim pTable As ITable
Set pTable = pFeatureWorkspace.OpenTable("MyLayers")

Dim pRow As IRow
Set pRow = pTable.CreateRow

pRow.Value(pRow.Fields.FindField("Layers")) = pMemoryStream
pRow.Store
End Sub

//读取
Private Sub UIButtonControl2_Click()
Dim pWorkspaceFactory As IWorkspaceFactory
Set pWorkspaceFactory = New AccessWorkspaceFactory

Dim pFeatureWorkspace As IFeatureWorkspace
Set pFeatureWorkspace =
pWorkspaceFactory.OpenFromFile("C:/Source/BLOB.mdb", 0)

Dim pTable As ITable
Set pTable = pFeatureWorkspace.OpenTable("MyLayers")

Dim pCursor As ICursor
Set pCursor = pTable.Search(Nothing, False)

Dim pRow As IRow
Set pRow = pCursor.NextRow

If (pRow Is Nothing) Then Exit Sub

Dim pMemoryStream As IMemoryBlobStream
Set pMemoryStream = pRow.Value(pRow.Fields.FindField("Layers"))

Dim pLayer As ILayer
Set pLayer = New FeatureLayer

Dim pPersist As IPersistStream
Set pPersist = pLayer

pPersist.Load pMemoryStream

Dim pMxDoc As IMxDocument
Set pMxDoc = ThisDocument

pMxDoc.FocusMap.AddLayer pLayer
End Sub

http://www.gissky.net/blog/user1/275/archives/2004/642.html