如何在LINQ中添加dateadd? [英] how to make dateadd in LINQ?

问题描述

我有此代码...

其中p.ProductID == product&& (p.PurchaseDate< DateTime.Now.AddDays(-56)&& p.PurchaseDate> DateTime.Now.AddDays(-49))

我执行了LINQ但出现了错误..

我用事件探查器捕获了查询，而where子句看起来像这样..

@ p8 =''2011-02-17 18:43:30.5500000''，@ p9 = 688，@ p10 =''2011-02-17 18:43:30.5530000''，...

这意味着DateTime.Now.AddDays过去了毫秒..
我只需要约会！

我想使用sql中的DateAdd函数.

我该怎么办?

请帮忙....

I have this code...

where p.ProductID == product && ( p.PurchaseDate < DateTime.Now.AddDays(-56) && p.PurchaseDate > DateTime.Now.AddDays(-49))

and I executed the LINQ but I got an error..

I caught the query with profiler and the where clause looked like this..

@p8=''2011-02-17 18:43:30.5500000'',@p9=688,@p10=''2011-02-17 18:43:30.5530000'',...

which means DateTime.Now.AddDays were passing milliseconds ..
I only need date!

I would like to use DateAdd function from sql.

how can I do that?

please help....

推荐答案

调用两次DateTime.Now，结果会不同毫秒.您必须缓存当前时刻:

Calling DateTime.Now two times, results to different milliseconds. You have to cache the current moment:

DateTime now = DateTime.Now;
DateTime fromDate = new DateTime( now.Year, now.Month, now.Day ).AddDays( -49 );
DateTime untilDate = new DateTime( now.Year, now.Month, now.Day ).AddDays( -56 );
...
where p.ProductID == product && ( p.PurchaseDate < untilDate && p.PurchaseDate > fromDate )

我不知道您的代码为什么不起作用(除了下面的 ** 1 )，但我相信这不是因为AddDays()方法，除非您的安装已损坏.

我刚刚进行了一些测试以确保.我正在检查其他两个日期之间的测试日期".

我创建了一个简单的表单，其中包含:
2个NumericUpDown控件(nudStart和nudEnd)用于定义要检查的日期范围.
1 DateTimePicker(dateTimePicker1)用于定义测试日期"
1 Button(btnGo)启动测试
1 TextBox(txtResult-启用MultiLine，WordWrap启用)以显示结果

这是我使用的代码:

I do not know why your code is not working (Except see **1 below) but I am confident that it is not because of a malfunction in the AddDays() method, unless your installation has become corrupted.

I have just run some tests to make sure. I am checking for a ''test date'' being between two other dates.

I created a simple Form containing:
2 NumericUpDown controls (nudStart and nudEnd) for defining the range of dates to check.
1 DateTimePicker (dateTimePicker1) for defining the ''test date''
1 Button (btnGo) to fire off the test
1 TextBox (txtResult - MultiLine on, WordWrap on) to display the outcome

Here is the code I used:

public partial class DateTimeTestForm : Form
{
    DateTime rangeStart = DateTime.MinValue;
    DateTime rangeEnd = DateTime.MaxValue;

    public DateTimeTestForm()
    {
        InitializeComponent();
    }

    private void ShowResult(bool isValid)
    {
        string resultString = "The test date {0:D} is{1} between {2:D} and {3:D}";

        this.txtResult.Text = string.Format(resultString, this.dateTimePicker1.Value,
            isValid ? "" : " NOT",
            rangeStart,
            rangeEnd);
    }

    private void btnGo_Click(object sender, EventArgs e)
    {
        ShowResult(this.dateTimePicker1.Value > rangeStart && this.dateTimePicker1.Value < rangeEnd);
    }

    private void nudStart_ValueChanged(object sender, EventArgs e)
    {
        this.rangeStart = DateTime.Now.AddDays((double)this.nudStart.Value);
    }

    private void nudEnd_ValueChanged(object sender, EventArgs e)
    {
        this.rangeEnd = DateTime.Now.AddDays((double)this.nudEnd.Value);
    }
}

如果您想自己尝试一下，则需要连接事件处理程序，将nudStart设置为-56并将nudEnd设置为-49，在DateTimePicker中选择要测试的日期(我在2011年2月4日和2011年2月8日进行了两次测试)然后单击btnGo.您会看到AddDays()正确设置了日期.

** 1 我注意到您正在检查PurchaseDate不在您的日期范围内.这是您想要的吗?

If you want to try this for yourself you will need to hook up the event handlers, set nudStart to -56 and nudEnd to -49, select a date to test in the DateTimePicker (I did two tests 4th Feb 2011 and 8th Feb 2011) then click btnGo. You will see that AddDays() correctly sets the dates.

**1 I notice that you are checking for the PurchaseDate being outside of your date range. Is this what you intended?

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