我必須顯示來自 xml 文件的聊天。但是當(dāng)我加入 2 個合并表時，會出現(xiàn)一些錯誤。錯誤是：無法將類型“System.Collections.Generic.IEnumerable”隱式轉(zhuǎn)換為“System.Collections.Generic.IEnumerable”。存在顯式轉(zhuǎn)換（您是否缺少演員表？） D:\ChatReport\ChatReport\Default.aspx.cs 109 42 ChatReport public void chatload2() { DataTable dtmsg = new DataTable(); DataTable dtmsgtxt = new DataTable(); DataTable dtmsgbody = new DataTable(); DataTable dtuserinfo = new DataTable(); DataTable dtnewparty = new DataTable(); DataTable dtbodyuser = new DataTable(); DataTable dtmerge = new DataTable(); XmlTextReader xmlreader = new XmlTextReader(Server.MapPath("chattest.xml")); DataSet ds = new DataSet(); ds.Locale = CultureInfo.InvariantCulture; ds.ReadXml(xmlreader); dtmsg = ds.Tables["message"]; dtmsgtxt = ds.Tables["msgText"]; dtuserinfo = ds.Tables["userInfo"]; dtnewparty = ds.Tables["newParty"]; dtbodyuser = dtnewparty.Copy(); dtbodyuser.Merge(dtuserinfo); dtbodyuser.Columns.Remove("timeShift"); dtbodyuser.Columns.Remove("eventid"); dtbodyuser.Columns.Remove("chatTranscript_Id"); dtbodyuser.Columns.Remove("personId"); //dtbodyuser.Columns.Remove("newParty_Id"); dtbodyuser.Columns.Remove("visibility"); dtbodyuser.AcceptChanges(); DataTable dt = dtbodyuser; dtmsgbody = dtmsg.Copy(); dtmsgbody.Merge(dtmsgtxt); dtmsgbody.AcceptChanges(); DataTable dt10 = new DataTable(); IEnumerable<DataRow> query = from dtquer in dtmsgbody.AsEnumerable() join dtusr in dtbodyuser.AsEnumerable() on dtquer.Field<string>("userId") equals dtusr.Field<string>("userId") select new
1 回答
猛跑小豬
TA貢獻1858條經(jīng)驗 獲得超8個贊
您專門為 DataRow 類型的 IEnumerable 調(diào)用，然后在其中選擇一個 IEnumerable 類型 Anonymous ——您需要指定匿名類型實際上是 DataRow 對象：
IEnumerable<DataRow> query = from dtquer in dtmsgbody.AsEnumerable()
join dtusr in dtbodyuser.AsEnumerable()
on dtquer.Field<string>("userId") equals
dtusr.Field<string>("userId")
select new DataRow
[
dtquer.Field<string>("userId"),
dtusr.Field<string>("userNick"),
dtquer.Field<int>("timeShift"),
dtquer.Field<int>("message_Id"),
dtquer.Field<string>("msgText_Text")
];
或者，使用“var”使“查詢”對象不那么具體，因此您選擇的類型可以決定 IEnumerable 的組成：
var query = from dtquer in dtmsgbody.AsEnumerable()
join dtusr in dtbodyuser.AsEnumerable()
on dtquer.Field<string>("userId") equals
dtusr.Field<string>("userId")
select new
{
userId = dtquer.Field<string>("userId"),
userNick = dtusr.Field<string>("userNick"),
timeShift = dtquer.Field<int>("timeShift"),
message_Id = dtquer.Field<int>("message_Id"),
msgText_Text = dtquer.Field<string>("msgText_Text")
};
盡管您稍后將在 CopyToDataTable() 的代碼中需要 DataRows，所以為了我的錢，我自己會采用第一種方法，而不是將“var”與我需要轉(zhuǎn)換的匿名類型一起使用。
編輯
為了回應(yīng)評論中提到的內(nèi)容，擺脫對 Copy() 的依賴可能是更好的解決方案。通過定義表結(jié)構(gòu)，然后將所需的值分配給適當(dāng)?shù)牧?，您可以繞過轉(zhuǎn)換問題。
DataTable dt10 = new DataTable();
dt10.Columns.Add("UserId");
dt10.Columns.Add("Nickname");
dt10.Columns.Add("TimeShift");
dt10.Columns.Add("MessageId");
dt10.Columns.Add("MessageText");
var query = from dtquer in dtmsgbody.AsEnumerable()
join dtusr in dtbodyuser.AsEnumerable()
on dtquer.Field<string>("userId") equals
dtusr.Field<string>("userId")
select new
{
userId = dtquer.Field<string>("userId"),
userNick = dtusr.Field<string>("userNick"),
timeShift = dtquer.Field<int>("timeShift"),
message_Id = dtquer.Field<int>("message_Id"),
msgText_Text = dtquer.Field<string>("msgText_Text")
};
var counter = 0;
foreach (var row in query)
{
dt10.NewRow();
var newRow = dt10.Rows[counter];
newRow.ItemArray[0] = row.userId;
newRow.ItemArray[1] = row.userNick;
newRow.ItemArray[2] = row.timeShift;
newRow.ItemArray[3] = row.message_Id;
newRow.ItemArray[4] = row.msgText_Text;
counter++;
}
// Should end up with dt10 having all the results from the query above loaded into it
沒有依賴項就很難檢查，但是您報告的初始錯誤不再顯示在我的 Visual Studio 中。
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