Linq动态选角问题

我想运行一个查询,以获取logType的不同“logName”项的字符串数组。以下方法效果很好:

Dim stringArray() As String = (From item In dc.Vw_Logs 
    Where item.LogType = [Passed in logType] 
    Select item.LogName Distinct).ToArray()

Dim q = From item In dc.Vw_Logs Distinct
If not logType is nothing Then 
    q = q.Where(Function(item) item.LogType = logType)
End If
q.Select(Function(item) item.LogName)
Dim stringArray() As String = q.ToArray()

Value of type '1-dimensional array of Vw_Log' cannot be converted 
to '1-dimensional array of String'