如何修復運算符'=='對於ulong和long類型的操作數不明確

Question

我目前正在Discord Server中建立一個新命令，並且正在努力將UserId轉換回服務器中的Users Nickname。

我收到錯誤消息運算符'=='在ulong和long類型的操作數上不明確

有人可以幫我弄清楚我做錯了什么

Int64 memberId = reader.GetInt64(0);
string name = Context.Guild.Users
    .Where(x => x.Id == memberId)
    .First()
    .Nickname != null 
        ? Context.Guild.Users.Where(x => x.Id = memberId).First().Nickname 
        : Context.Guild.Users.Where(x => x.Id = memberId).First().Username;
Int64 votes = reader.GetInt64(2);
GOTWVote.Add($@"{name} has received {votes} vote(s)");

Answer 1

在.Where(x => x.Id = memberId) ，應該像以前一樣使用==進行比較，而不是= （歸因）。

Int64 memberId = reader.GetInt64(0);
string name = Context.Guild.Users
    .Where(x => x.Id == memberId)
    .First()
    .Nickname != null 
        ? Context.Guild.Users.Where(x => x.Id == memberId).First().Nickname 
        : Context.Guild.Users.Where(x => x.Id == memberId).First().Username;
Int64 votes = reader.GetInt64(2);
GOTWVote.Add($@"{name} has received {votes} vote(s)");

但是您可以將此代碼重構為此（請閱讀注釋）：

var memberId = reader.GetInt64(0);
// search for the user just a single time!
var user = Context.Guild.Users.First(x => x.Id == memberId);

// apply the rule to define the name string
string name = @string.IsNullOrEmpty(user.Nickname) ? user.Nickname : user.Username;

var votes = reader.GetInt64(2);
GOTWVote.Add($@"{name} has received {votes} vote(s)");

Answer 2

嘗試將memberId轉換為ulong （或UInt64 ），以便類型匹配x.Id ：

var memberId = (ulong)reader.GetInt64(0);
string name = Context.Guild.Users
    .Where(x => x.Id == memberId)
    ...
    ...

此外，您還需要解決其他一些問題，如其他答案和評論所建議的那樣。 ;）

Answer 3

第一步是強制轉換以解決歧義運算符。 接下來，重新安排您的查詢以擺脫兩個額外的子查詢：

Int64 memberId = reader.GetInt64(0);
var user = Context.Guild.Users
    .Where(x => x.Id == (UInt64)memberId)
    .First();

string name = 
    user.Nickname != null 
        ? user.Nickname 
        : user.Username;

Int64 votes = reader.GetInt64(2);
GOTWVote.Add($@"{name} has received {votes} vote(s)");