No size set for variable length data type: String

when try to insert an empty string to oracle through .Net, it would through an error like this:No size set for variable length data type: String.  It occured cause oracle does not treat empty string as null in database, it need to be instead by System.DBNull in DotNet.

原因,在Oracle中,不支持插入0长度的字符串,必须将该参数的值设置为null,问题就解决了。这个和SQL Server是不一样的。