如何修复运算符 '==' 在 ulong 和 long 类型的操作数上不明确

Question

我目前正在我的 Discord 服务器中构建一个新命令，我正在努力将 UserId 转换回我服务器中的用户昵称。

我收到错误消息运算符“==”在 ulong 和 long 类型的操作数上不明确

谁能帮我弄清楚我做错了什么

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) 中，您应该使用== 进行比较，而不是像以前那样使用=（归因）。

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)");

但是你可以将这段代码重构为这个（读到 cmets）：

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

尝试将memberId 转换为ulong（或UInt64），以便类型匹配x.Id：

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

此外，正如其他答案和 cmets 所建议的那样，您还有一些其他问题需要解决。 ;)

Answer 3

第一步是通过强制转换来解决歧义运算符。接下来，重新排列查询以去除两个额外的子查询：

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)");