PipelineComponent.PreExecute 方法

public:
 virtual void PreExecute();

public virtual void PreExecute();

abstract member PreExecute : unit -> unit
override this.PreExecute : unit -> unit

Public Overridable Sub PreExecute ()

示例

以下示例展示了如何定位 中 InputColumnCollection列的列索引。 它们存储在本地变量中，然后用于 ProcessInput 访问 中的列 PipelineBuffer。

int[] bufferColumnIndex;  
public override void PreExecute()  
{  
    IDTSInput100 input = ComponentMetaData.InputCollection[0];  
    bufferColumnIndex = new int[input.InputColumnCollection.Count];  
    for ( int x=0; x < input.InputColumnCollection.Count; x++)  
    {  
        bufferColumnIndex[x] = BufferManager.FindColumnByLineageID( input.Buffer, input.InputColumnCollection[x].LineageID);  
    }  
}  
public override void ProcessInput( int inputID, PipelineBuffer buffer )  
{  
    while( buffer.NextRow() )  
    {  
        for( int x=0; x < bufferColumnIndex.Length(); x++ )  
        {  
            if( !buffer.IsNull(bufferColumnIndex[x]))  
            {  
                // TODO: Access the column data.  
            }  
        }  
    }  
}  

Private bufferColumnIndex As Integer()   

Public Overrides Sub PreExecute()   
 Dim input As IDTSInput100 = ComponentMetaData.InputCollection(0)   
 bufferColumnIndex = New Integer(input.InputColumnCollection.Count - 1) {}   
 Dim x As Integer = 0   
 While x < input.InputColumnCollection.Count  
   bufferColumnIndex(x) = BufferManager.FindColumnByLineageID(input.Buffer, input.InputColumnCollection(x).LineageID)   
   x -= 1  
 End While   
End Sub   

Public Overrides Sub ProcessInput(ByVal inputID As Integer, ByVal buffer As PipelineBuffer)   
 While buffer.NextRow   
   Dim x As Integer = 0   
   While x < bufferColumnIndex.Length   
     If Not buffer.IsNull(bufferColumnIndex(x)) Then   
     End If   
     x -= 1  
   End While   
 End While   
End Sub  

注解

组件开发者应尽可能多地考虑功能， PreExecute 因为它被调用的是每个组件一次，而不是每个缓冲 ProcessInput区一次。 组件应通过调用 FindColumnByLineageIDBufferManager的方法来定位输入和输出列的PipelineBuffer索引。