LINQ其中有四个与放大器条款;&安培; [英] LINQ Where clause with four &&

问题描述

我想在WHERE子句中有4个参数来创建一个LINQ查询。这是一个Windows 8应用项目，我使用的是SQLite数据库。 （ SQLite的实施）

I'm trying to create an LINQ Query with 4 arguments in the Where clause. It's a Windows 8 App project and I'm using an SQLite Database. (SQLite implementation )

这里的代码片段：

public List<FinancialListBoxExpenseItem> retrieveExpenseItems(int month, int year, bool isPaid, StaticResources.FrequencyEnum frequencyEnum)
{
    List<FinancialListBoxExpenseItem> tmpList = null;

    connection.RunInTransaction(() =>
    {
        var items = from s in connection.Table<FinancialListBoxExpenseItem>()
                    where (s.expenseDateNextPayment.Month == month)
                       && (s.expenseDateNextPayment.Year == year)
                       && (s.expensePaidForCurrentPeriod == isPaid)
                       && (s.expenseFrequencyTypeEnum == frequencyEnum)
                    select s;
        tmpList = items.ToList<FinancialListBoxExpenseItem>();
    });

    return tmpList;
}

它抛出一个NotSupportedAction：成员访问失败编译表达异常

It throws a NotSupportedAction: Member access failed to compile expression Exception

我不知道这是什么意思，我应该如何解决这个问题。

I have no idea what does this mean and how i'm supposed to fix it.

编辑：它作品，未经where子句因此，错误也必须在代码

it works without the where clause therefore the error must be related to this where clause part of the code

推荐答案

这是与此有关我怎么解决这个问题：

This is how i solved the problem:

public List<FinancialListBoxExpenseItem> retrieveExpenseItems(int month, int year, bool isPaid, StaticResources.FrequencyEnum frequencyEnum)
{
    List<FinancialListBoxExpenseItem> tmpList = new List<FinancialListBoxExpenseItem>();

    connection.RunInTransaction(() =>
    {
        var items = from s in connection.Table<FinancialListBoxExpenseItem>()
                    let convertedDate = (DateTime)s.expenseDateNextPayment
                    where (convertedDate.Month == month)
                       && (convertedDate.Year == year)
                       && (s.expensePaidForCurrentPeriod == isPaid)
                       && (s.expenseFrequencyTypeEnum == frequencyEnum)
                    select s;
        tmpList = items.ToList();
    });

    return tmpList;
}

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