單行上的Linq更新查詢？

Question

我正在嘗試在單個行的列上執行簡單的UPDATE。我收到Sequence contains no elements例外。

private void InsertUpdateFileLocation(string targetFileLocationAndFullName, 
    tbFileAttachment linkGuid) 
{ 
    ISESEntities context = new ISESEntities(); 

    var query = (from f in context.tbFileAttachments 
       where f.CCCPGUID == linkGuid.CCCPGUID 
       select f).First(); 

    query.FileLocation = targetFileLocationAndFullName; 

    context.SaveChanges(); 
} 

Answer 1

在這種情況下，您沒有與您正在搜索的值匹配的記錄。您可以通過使用FirstOrDefault趕上這則空測試：

var query = (from f in context.tbFileAttachments 
      where f.CCCPGUID == linkGuid.CCCPGUID 
      select f).FirstOrDefault(); 

if(query==null) 
{ 
    //no match found! 
}