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c#linqdatetimeequalsdynamic-linq
Vlad i Slav
Vlad i Slav

Reputation: 61

How to set DateTime equals method with Dynamic Linq in C#?

I need to filter data with Dynamic LINQ by DateTime field.

I'm try doing this like:

public class MyClass
{
    private DateTime datetime_field;
    //...
    //some other fields
    //...
}

public void MyMethod(string where_clause)
{
    List<MyClass> myData = new List<MyClass>()
    {
        //...
        //initialization
        //...
    };
    var query = myData.Where(where_clause).ToList();
    myDataGridView.DataSource = query;
}

// usage
string value = DateTime.Now.ToString(); // for example
if (DateTime.TryParse(value, out DateTime dt))
    MyMethod("datetime_field == DateTime(" + dt.Year + ", " + dt.Month + ", " + dt.Day + ", " + dt.Hour + ", " + dt.Minute + ", " + dt.Second + ")");

But the query return zero records. But if i set compare method >= or <= instead ==, query returns needed records amount.
Maybe I'm doing something wrong?

UPDATE:
I found example here: https://stackoverflow.com/a/26450835/7760805, but I'm still search a better solution.

UPDATE:
Solved by Stef Heyenrath.

Upvotes: 0

Views: 1588

Answers (3)

Stef Heyenrath
Stef Heyenrath

Reputation: 9860

Depending on the accuracy you need, you could just use the >= and < operators together, like this:

var date = DateTime.Now;

// accuracy is 1 day in this example
var from = date.Date;
var to = from.AddDays(1);

// If you only need to select on a day, use this:
var result = query.Where("datetime_field >= @0 && datetime_field < @1", from, to);

Upvotes: 3

Cameron Wilby
Cameron Wilby

Reputation: 2310

You should pass a string into the MyMethod method, then convert to DateTime and remove milliseconds within the method.

public class MyClass
{
    public DateTime datetime_field; // note this needs to be public, not private
}

public void MyMethod(string strDate)
{
    if (DateTime.TryParse(value, out DateTime dt))
    {
        List<MyClass> myData = new List<MyClass>()
        {
            // initialization
        };

        var roundedDate = new DateTime(dt.Year, dt.Month, dt.Day,
                                       dt.Hour, dt.Minute, dt.Second);

        var query = myData.Where(obj => obj.date_time == roundedDate).ToList();

        myDataGridView.DataSource = query;   
    }
}

// usage
string value = DateTime.Now.ToString();
MyMethod(value);

Upvotes: 3

Gabriel Scavassa
Gabriel Scavassa

Reputation: 594

What is the content of MyMethod ?

Try using the $ string builder.

MyMethod($"datetime_field == {new DateTime(dt.Year, dt.Month, dt.Day, dt.Hour, dt.Minute , dt.Second)}");

OR

MyMethod($"datetime_field == {dt.ToString())}");

I think its a problem with your logic not how you are constructing or passing datetime parameter.

Upvotes: -1

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