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Expression Lambda to order fields with null value


Expression Lambda to order fields with null value

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Expression Lambda to order fields with null value
Tag : vb.net , By : user171752
Date : November 23 2020, 01:01 AM

Hope that helps You can change your toStr expression to include a Coalesce operation where the right expression is a constant. Note that the left expression needs to be reference type (or a nullable value type) so you also need to ensure that the property type is not a value type.
Here's an example that should work:
Dim toStr As Expression = Expression.Call(
    If(pinfo.PropertyType.IsValueType, expr, Expression.Coalesce(expr, Expression.Constant(String.Empty))),
    "ToString",
    Nothing
)

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Lambda Expression to Group by 3 different Fields only when not null and count()


Tag : development , By : jsmb
Date : March 29 2020, 07:55 AM
wish help you to fix your issue Here's the model I have. , The following will work.
 var notificationCount = db.Notifications
      .GroupBy(x => new { x.CommentID, x.ProjectID, x.BookID, x.NotificationTypeID })
      .Count();

Lambda Expression : How to Concat 2 Fields?


Tag : asp.net-mvc , By : Ben Brown
Date : March 29 2020, 07:55 AM
wish helps you You rock! Thank you very much for your great help. Actually I have encountered "LINQ to Entities does not recognize the method 'System.String Format(System.String, System.Object, System.Object)' method, and this method cannot be translated into a store expression." error message after first applying your method, but by adding ".ToList()" to the third line I have succeeded. So, for informing those who might need this great functionality here is the last state of the method in my Controller:
private void PopulateMeetingsDropDownList(object selectedMeetings = null)
{
    var meetingsQuery = repository.Meetings.ToList()
        .Join(repository.Cities, m => m.MeetingCityId, c => c.CityID,
                (m, c) => new
                {
                    CityID = c.CityID,
                    DisplayValue = string.Format("{0} ({1:dd MMMM yyyy})", c.CityName, m.MeetingStartDate) 
                })
       .OrderBy(x => x.CityID).ToList();
    ViewData["MeetingId"] = new SelectList(meetingsQuery, "CityID", "DisplayValue", selectedMeetings); 
}

Order By in List<T> with Lambda Expression when foreign key is null


Tag : chash , By : itsmegb
Date : March 29 2020, 07:55 AM
I hope this helps . You can extend your lambda expression or using c# 6 features:
// use c# 6.0 ?. operator
listData = db.db_table
             .OrderBy(x => x.db_table1?.column_name)
             .ToList();

// check value manually
listData = db.db_table
             .OrderBy(x => x.db_table1 != null ? x.db_table1.column_name : string.Empty)
             .ToList();

// filter null values before sorting
listData = db.db_table
             .Where(x => x.db_table1 != null)
             .OrderBy(x => x.db_table1.column_name)
             .ToList();

python lambda expression with dynamic fields


Tag : python , By : snapshooter
Date : March 29 2020, 07:55 AM
hope this fix your issue You need an all function which is only true if every element of an iterable is True. Otherwise every input to your filter was returning True.
list(filter(lambda d: all(d[field] == reference_row[field] for field in compare_fields), my_list))
[d for d in my_list if 
 all(d[field] == reference_row[field] for field in compare_fields)]

Is there a C# syntax for a 'null' lambda expression? eg, calling OrderBy(x => x) without the lambda expression?


Tag : chash , By : Ed.
Date : March 29 2020, 07:55 AM
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