我在SQL数据库表中使用了带有2个字段的select Disctinct语句。这是我的代码。

myCommand = New SqlCommand("SELECT DISTINCT Author FROM tblBook UNION SELECT DISTINCT BookCode FROM tblBook",myConnection)
 myAdapter = New SqlDataAdapter(myCommand)
 myAdapter.Fill(myDataSet, "tblBook")
 cboAuthor.DataSource = myDataSet.Tables(0)
 cboAuthor.DisplayMember = "Author"
 cboAuthor.DisplayValue = "BookCode"

并产生错误：cannot bind to the new member. Parameter name:value。请帮忙