I have a Linq query which is selecting 2 columns(that can be any 2 from all columns) dynamically based on some condition.I need to map the query result in to below model irrespective of selected column names
public class FinalModel
{
public string Text { get; set; }
public string Id { get; set; }
}
Currently I am using reflection to map the result in to that model because i am getting some anonymous list of objects and it is working fine, But I want to remove that reflection and need to add the mapping in the select itself, my current implementation is like below
string column1 = "Name" //can be other columns also
string column2 = "Age"
var result = _context.table1
.Select("new ("+ column1 +","+ column2 +")")
.Distinct()
.Take(10) // having more records in table
.ToDynamicList()
.Select(x => new FinalModel()
{
Id = x.GetType().GetProperty(column1).GetValue(x).ToString(),
Text = x.GetType().GetProperty(column2).GetValue(x).ToString(),
});
The above code is working fine but I need to remove the below section
.Select(x => new FinalModel()
{
Id = x.GetType().GetProperty(column1).GetValue(x).ToString(),
Text = x.GetType().GetProperty(column2).GetValue(x).ToString(),
});
Is there any way to remove the refletion and add that model mapping directly inside Select("new (column1,column2)")
Is there any way to add orderBy with Column2 variable?
You can use generic versions of Select and ToDynamicList and OrderBy($"{column2}") for sorting:
var result = _context.table1
.Select<FinalModel>($"new ({column1} as Id, {column2} as Text)")
.Distinct()
.OrderBy("Text")
.Take(10)
.ToDynamicList<FinalModel>();
Or if you want to stick with dynamic:
var result = _context.table1
.Select($"new ({column1}, {column2})")
.Distinct()
.OrderBy($"{column2}")
.Take(10)
.ToDynamicList()
.Select(d => new FinalModel()
{
Id = d[column1].ToString(),
Text = d[column2].ToString(),
})
.ToList();
You need to use .Select<T> instead of just .Select() to make sure that the selected entity the correct type. So in your case you need .Select<FinalModel>.
Use the as cast operator to "rename" the properties from the source-entity to the destination entity (FinalModel)
If you want the result to be typed, also use .ToDynamicList<FinalModel>().
Full example code below:
using System.Linq.Dynamic.Core;
class Program
{
static void Main(string[] args)
{
var myQuery = new[] { new XModel { Age = "1", Name = "n" } }.AsQueryable();
string column1 = "Name";
string column2 = "Age";
var result = myQuery
.Select<FinalModel>("new (" + column1 + " as Id, " + column2 + " as Text)")
.Distinct()
.Take(10)
.ToDynamicList<FinalModel>();
Console.WriteLine(result[0].Id + " " + result[0].Text);
}
public class XModel
{
public string Name { get; set; }
public string Age { get; set; }
}
public class FinalModel
{
public string Text { get; set; }
public string Id { get; set; }
}
}
Related
Using EF Core code-first, and I want to find any record with a similar list of a foreign entities to the entity I already have.
public class ClownModel {
public int Id { get; set; }
public List<CarModel> Cars { get; set; }
}
public class CarModel {
public int Id { get; set; }
}
var MyClown = new ClownModel() { /*add properties*/ }
//or maybe an existing record selected from database, just some ClownModel instance
Basically, "Select all the ClownModels where they have any Cars.Id that are in my MyClown.Cars"
Assuming that ClownModel has unique CarModel Id's, you can use the following query:
Matches All Ids
var ids = MyClown.Cars.Select(c => c.Id).ToList();
var query =
from cm in ctx.ClownModel
where cm.Cars.Where(c => ids.Contains(c.Id)).Count() == ids.Count
select cm;
Matches Any Ids
var ids = MyClown.Cars.Select(c => c.Id).ToList();
var query =
from cm in ctx.ClownModel
where cm.Cars.Where(c => ids.Contains(c.Id)).Any()
select cm;
I want to concatenate DateTime field and string field in MVC application.
I want Linq to Entities query to solve this. Here is my SQL query which I want in Linq.
Select accountid,TourID, ' ('+ convert(nvarchar(20), fromdate ,105) +')' + purpose as TourDetails
from Tour
where AccountID=#AccID;
As shown in above query I want to concat fromdate and purpose. I want to pass result of this query as JSON result.
Something like this:
public class Tour
{
public int accountid { get; set; }
public int TourID { get; set; }
public DateTime date { get; set; }
public string purpose { get; set; }
}
var t = new List<Tour>
{
new Tour
{
accountid = 1,
TourID = 2,
date = DateTime.Now,
purpose = "Testing"
}
};
var output = t.Where(c => c.accountid == accId).Select(k => new
{
accountid = k.accountid,
TourID = k.TourID,
TourDetails = k.date.ToString() + k.purpose
}).ToList();
var o = JsonConvert.SerializeObject(output);
You can use something like this if you're in a MVC Controller requiring an ActionResult as output :
//here 'context' is your DbContext implementation and Tours is your DbSet.
var TourDetails= context.Tours.Where(t=>t.AccountID==_AccID)
.Select(s=>new {
AccountID = s.accountid,
TourID = s.TourID,
//s.fromdate.ToString("yyyyMMddHHmmss") use this to format your date if needed
TourDetails = s.fromdate.ToString() + s.purpose
})
.ToList();
//JsonRequestBehavior.AllowGet only if your not using POST method
return Json(TourDetails, JsonRequestBehavior.AllowGet);
I am having a class Item.
class Item{
public int Id { get; set; }
public DateTime CreatedDate { get; set; }
public string Name { get; set; }
public string Description { get; set;}
}
I want to filter list of items based on dynamic column name.
Suppose I want list of Names then Column Name is "Name" and result will be list of names
If column name is Description, I need list of descriptions.
How to do this with LinQ?
Easy, just select the property you need from the list:
var items = new List<Item>();
//get names
var names = items.Select(x => x.Name);
//get descriptions
var descriptions = items.Select(x => x.Description);
Update:
You'll need a bit of reflection to do this:
var names = items.Select(x => x.GetType().GetProperty("Name").GetValue(x));
Throw this in a method for re-usability:
public IEnumerable<object> GetColumn(List<Item> items, string columnName)
{
var values = items.Select(x => x.GetType().GetProperty(columnName).GetValue(x));
return values;
}
Of course this doesn't validate wether the column exists in the object. So it will throw a NullReferenceException when it doesn't. It returns an IEnumerable<object>, so you'll have to call ToString() on each object afterwards to get the value or call the ToString() in the query right after GetValue(x):
public IEnumerable<string> GetColumn(List<Item> items, string columnName)
{
var values = items.Select(x => x.GetType().GetProperty(columnName).GetValue(x).ToString());
return values;
}
Usage:
var items = new List<Item>(); //fill it up
var result = GetColumn(items, "Name");
I've written a LINQ query shown below :
List<Actions> actions = resourceActions.Actions.Select(s => s.ActionName).ToList();
How do I give for selecting multiple columns here ? ie I want to add columns s.ActionId and s.IsActive. I'm unable to apply it.
Make a class to represent the data you want:
public class ResourceAction
{
public int Id {get;set;}
public string Name {get; set; }
}
Select a list of those instead:
List<ResourceAction> actions = resourceActions.Actions
.Select(s => new ResourceAction() { Id = s.Id, Name = s.ActionName}).ToList();
I believe this is what your looking for. However you need to change the output to an anonymous type.
var actions = resourceActions.Actions.Select(s => new { s.ActionName, s.ActionId, s.IsActive } ).ToList();
You can use a anonymous type for this, for example
var actions = resourceActions.Actions.Select(s =>
new { Id = s.Id, Name = s.ActionName, Active = s.IsActive).ToList();
but a better way would be to create a class like
public class ActionWithId
{
public int Id { get; set; }
public string Name { get; set; }
public bool Active { get; set; }
}
List<ActionWithId> actions = resourceActions.Actions.Select(s =>
new ActionWithId() { Id = s.Id, Name = s.ActionName, Active = s.IsActive }).ToList();
I have a method that selects two fields from database where text in first field match some value
public static List<List<string>> SelectForSearch(string letter)
{
var data = (from p in model.City
where p.Name.StartsWith(letter)
select new List<string> { p.Name, p.CountryName }).ToList();
return data;
}
But it returns me a list like this:
[0][0]Australia
[0][1]Ballina
[1][0]Berry
[1][1]Australia
[2][0]Australia
[2][1]Bendigo
...
Country and City possition don't have a static index like this:
[0][0]Ballina
[0][1]Australia
[1][0]Berry
[1][1]Australia
[2][0]Bendigo
[2][1]Australia
...
Your issue is that in your select statement, instead of creating a type with Name and CountryName you are creating a List of strings. The List initialiser allows you to pass in the values when the list is constructed by placing them in { } and you are using this ability by accident, as you saw it creates a list of strings where the name is the first element and the country name is the second element. What you want to be doing is more like:
var data = (from p in model.City
where p.Name.StartsWith(letter)
select new { City = p.Name, CountryName = p.CountryName }).ToList();
return data;
This is using anonymous types which is not good as you want to declare a type for the return value. So you should really create a class for storage, for example:
public class CityCountryPair
{
public String City { get; set; }
public String CountryName { get; set; }
}
then your method becomes
public static List<CityCountryPair> SelectForSearch(string letter)
{
var data = (from p in model.City
where p.Name.StartsWith(letter)
select new CityCountryPair() { City = p.Name,
CountryName = p.CountryName
}).ToList();
return data;
}