WPF C# LINQ：运算符“&&”不能应用于“字符串”和“字符串”查询类型的操作数
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WPF C# LINQ: Operator '&&' cannot be applied to operands of type 'string' and 'string' query
提问by kknaguib
I'm trying to execute this query but for some reason it doesn't like the fact that 2 strings are sitting beside each other, here's the query:
我正在尝试执行此查询，但由于某种原因，它不喜欢 2 个字符串并排放置的事实，这是查询：
var FiveSecStatsQuery = from qai in connection.QuickAnalyzerInputs
join calP in connection.CalculatedPrices on qai.InputID equals calP.TradeID
where ***(qai.ClientName = clientName) && (qai.CurrencyPair = cur_pair)***
&& (calP.Description = PriceDescriptions.FiveSeconds) && (calP.Outcome != null)
select new
{
calP.Outcome
};
The error is : Operator '&&' cannot be applied to operands of type 'string' and 'string'
错误是：运算符“&&”不能应用于“字符串”和“字符串”类型的操作数
Why is it giving me this error? Both ClientName and CurrencyPair are of type string in the database. The error occurs where the asterisks are
为什么给我这个错误？ClientName 和 CurrencyPair 在数据库中都是字符串类型。错误发生在星号所在的位置
回答by Habib
You need double ==, not single =so your whereclause should be:
你需要 double ==，而不是 single ，=所以你的where条款应该是：
where (qai.ClientName == clientName) && (qai.CurrencyPair == cur_pair)
&& (calP.Description == PriceDescriptions.FiveSeconds) && (calP.Outcome != null)
回答by Tamir Vered
Change (qai.ClientName = clientName) && (qai.CurrencyPair = cur_pair)to (qai.ClientName == clientName) && (qai.CurrencyPair == cur_pair)since its boolean operation not value assignment
更改(qai.ClientName = clientName) && (qai.CurrencyPair = cur_pair)为(qai.ClientName == clientName) && (qai.CurrencyPair == cur_pair)因为它的布尔运算不是赋值
