Develop Reference

How to convert key value pair to a custom object list

enter image description hereI have a keyValupair of Hotel details;:
//This is where the data comes from : -
JavaScriptSerializer json_serializer = new JavaScriptSerializer();
dynamic hotels1 = (dynamic)json_serializer.DeserializeObject(jso);
var keyValuePairs = hotels1["hotels"];
var hotelList = keyValuePairs["hotels"]; // hotelList[0] ={'key'='Code' ;value='123'}
//{'key'='Name'
// ;value='Sheraton'}
how do i convert this to a list of Hotel
List<Hotel> hotaals = new List<Hotel>();
where Hotel is
public class Hotel
{
public int code { get; set; }
public string name { get; set; }
}
I use a for loop to map fields, but my great boss says its inefficient and i have to use Linq.
The loop i use
foreach (dynamic h in hotelList)
{
oneHotel = new Hotel();
oneHotel.code = h["code"];
oneHotel.name = h["name"];
myHotels.Add(oneHotel);
}

Well the brute force way would be to just project the dictionary to objects by hard-coding the properties:
List<Hotel> hotaals = hotelList.Select(kvp => new Hotel {
code = kvp['Code'],
name = kvp["Name"]
})
.ToList();
I would also challenge what your "great boss" means by inefficient".

So first you get your initial data:
var hotelList = keyValuePairs["hotels"];
Then use linq to create your new list:
var hotelObjects = hotelList.Select(hotel => new Hotel { code = hotel.key, name = hotel.name});
Now to be clear what linq is doing under the hood is an iterative loop through the objects (just like foreach) and creates a new Hotel object for each item in the hotelList and returns them as an IQueryable<Hotel>. Just apply .ToArray() or .ToList() if you don't want an IQueryable<>
Now from what it sounds like your initial List of hotel details isn't structured so you might have to modify my supplied linq query above to suit the structure of the list.
You may need something closer to this:
// Gives IQueryable<Hotel> as result
var hotelObjects = hotelList.Select(hotel => new Hotel{code = hotel["key"], name = hotel["name"]});
// Gives Array<Hotel> as result
var hotelObjects = hotelList.Select(hotel => new Hotel{code = hotel["key"], name = hotel["name"]}).ToArray();
// Gives List<Hotel> as result
var hotelObjects = hotelList.Select(hotel => new Hotel{code = hotel["key"], name = hotel["name"]}).ToList();

Select Distinct User ID in a ViewModel List

I'm pretty new to MVC so there might be a super simple answer to this.
The following is my current controller code:
public class StudentBanController : Controller
{
SWGS_GlobalDataEntities DataContext = new SWGS_GlobalDataEntities();
// GET: StudentBan
public ActionResult DisplayBans()
{
var theData = DataContext.tblGlobalLogOnLogOffStudentBans.ToList();
List<StudentBanDisplayViewModel> BanList = theData
.Select(viewModel => new StudentBanDisplayViewModel
{
ID = viewModel.ID,
UserID = viewModel.UserID,
StartBan = viewModel.StartBan,
EndBan = viewModel.EndBan
}).Where(b => b.EndBan > DateTime.Today).ToList();
return PartialView(BanList);
}
}
What I am trying to do is create a list, but I only want it to contain records for Distinct UserID's and I cant figure how to do it.
I have tried .distinct in various places and also grouping by user ID and selecting .first but nothing seems to do the job.
Any advice?

Try the following
List<StudentBanDisplayViewModel> BanList = theData
.Select(viewModel => new StudentBanDisplayViewModel
{
ID = viewModel.ID,
UserID = viewModel.UserID,
StartBan = viewModel.StartBan,
EndBan = viewModel.EndBan
}).Where(b => b.EndBan > DateTime.Today)
.DistinctBy(s => new {s.UserID}).ToList();
How to remove duplicates from collection using IEqualityComparer, LinQ Distinct
You will require the following
https://code.google.com/p/morelinq/source/browse/MoreLinq/DistinctBy.cs?r=d4396b9ff63932be0ab07c36452a481d20f96307

Populating Dropdown using Reflection

I am using MVC4 and what I want to do is use a dropdown connected to my search box to search for the selected property. How would I am stuck on the Text= prop.Name. How could I go through and access all of the properties using this.
My Controller
public ActionResult SearchIndex(string searchString)
{
var selectListItems = new List<SelectListItem>();
var first = db.BloodStored.First();
foreach(var item in first.GetType().GetProperties())
{
selectListItems.Add(new SelectListItem(){ Text = item.Name, Value = selectListItems.Count.ToString()});
}
IEnumerable<SelectListItem> enumSelectList = selectListItems;
ViewBag.SearchFields = enumSelectList;
var bloodSearch = from m in db.BloodStored
select m;
if (!String.IsNullOrEmpty(searchString))
{
bloodSearch = bloodSearch.Where(s => string.Compare(GetValue(s, propertyName), searchString) == 0);
}
return View(bloodSearch);
}
The selectlist is working now I just need to go over my searchstring and how to pass two parameters now.

I'm not quite sure what you're asking. If you want to create a list of objects with the property Text set to the property name of the object, you could get the first object in the BloodStored enumerable and create a list of anonymous types:
// Get one instance and then iterate all the properties
var selectListItems = new List<object>();
var first = db.BloodStore.First();
foreach(var item in first.GetType().GetProperties()){
selectListItems.Add(new (){ Text = item.Name});
}
ViewBag.SearchFields = selectListItems;

Cannot implicitly convert type '.List<AnonymousType#1>' to '.List<WebApplication2.Customer>'

In the following code that returns a list:
public List<Customer> GeAllCust()
{
var results = db.Customers
.Select(x => new { x.CustName, x.CustEmail, x.CustAddress, x.CustContactNo })
.ToList()
return results;
}
I get an error reporting that C# can't convert the list:
Error: Cannot implicitly convert type System.Collections.Generic.List<AnonymousType#1> to System.Collections.Generic.List<WebApplication2.Customer>
Why is that?
Here's a screenshot showing some additional information that Visual Studio provides in a tooltip for the error:
Is it right way to return some columns instead of whole table....?
public object GeAllCust()
{
var results = db.Customers.Select(x => new { x.CustName, x.CustEmail, x.CustAddress, x.CustContactNo }).ToList();
return results;
}

When you look the code:
x => new { ... }
This creates a new anonymous type. If you don't need to pull back only a particular set of columns, you can just do the following:
return db.Customers.ToList();
This assumes that Customers is an IEnumerable<Customer>, which should match up with what you are trying to return.
Edit
You have noted that you only want to return a certain subset of columns. If you want any sort of compiler help when coding this, you need to make a custom class to hold the values:
public class CustomerMinInfo
{
public string Name { get; set; }
public string Email { get; set; }
public string Address { get; set; }
public int? ContactNumber { get; set; }
}
Then change your function to the following:
public List<CustomerMinInfo> GetAllCust()
{
var results = db.Customers.Select(x => new CustomerMinInfo()
{
Name = x.CustName,
Email = x.Email,
Address = x.Address,
ContactNumber = x.CustContactNo
})
.ToList();
return results;
}
This will work, however, you will lose all relationship to the database context. This means if you update the returned values, it will not stick it back into the database.
Also, just to repeat my comment, returning more columns (with the exception of byte arrays) does not necessarily mean longer execution time. Returning a lot of rows means more execution time. Your function is returning every single customer in the database, which when your system grows, will start to hang your program, even with the reduced amount of columns.

You are selecting to an anonymous type, which is not a Customer.
If you want to do (sort of) this, you can write it like this:
return db.Customers.Select(x => new Customer { Name = x.CustName, Email = x.CustEmail, Address = x.CustAddress, ContactNo = x.ContactNo }).ToList();
This assumes the properties on your Customer object are what I called them.
** EDIT ** Per your comment,
If you want to return a subset of the table, you can do one of two things:
Return the translated form of Customer as I specified above, or:
Create a new class for your business layer that only has only those four fields, and change your method to return a List<ShrunkenCustomer> (assuming ShunkenCustomer is the name that you choose for your new class.)

GetAllCust() is supposed to return a List of Customer, Select New will create a list of Anonymous Types, you need to return a list of Customer from your query.
try:
var results = db.Customers.Select( new Customer{CustName = x.CustName}).ToList(); //include other fields

I guess Customer is a class you have defined yourself?
The my suggestion would be to do something like the following:
var results = db.Customers.Select(x => new Customer(x.Custname, x.CustEmail, x.CustAddress, x.CustContactNo)).ToList();
The reason is that you are trying to return a list of Customer but the results from your link is an anonymous class containing those four values.
This would of course require that you have a constructor that takes those four values.

Basically whatever u got in var type, loop on that and store it in list<> object then loop and achieve ur target.Here I m posting code for Master details.
List obj = new List();
var orderlist = (from a in db.Order_Master
join b in db.UserAccounts on a.User_Id equals b.Id into abc
from b in abc.DefaultIfEmpty()
select new
{
Order_Id = a.Order_Id,
User_Name = b.FirstName,
Order_Date = a.Order_Date,
Tot_Qty = a.Tot_Qty,
Tot_Price = a.Tot_Price,
Order_Status = a.Order_Status,
Payment_Mode = a.Payment_Mode,
Address_Id = a.Address_Id
});
List<MasterOrder> ob = new List<MasterOrder>();
foreach (var item in orderlist)
{
MasterOrder clr = new MasterOrder();
clr.Order_Id = item.Order_Id;
clr.User_Name = item.User_Name;
clr.Order_Date = item.Order_Date;
clr.Tot_Qty = item.Tot_Qty;
clr.Tot_Price = item.Tot_Price;
clr.Order_Status = item.Order_Status;
clr.Payment_Mode = item.Payment_Mode;
clr.Address_Id = item.Address_Id;
ob.Add(clr);
}
using(ecom_storeEntities en=new ecom_storeEntities())
{
var Masterlist = en.Order_Master.OrderByDescending(a => a.Order_Id).ToList();
foreach (var i in ob)
{
var Child = en.Order_Child.Where(a => a.Order_Id==i.Order_Id).ToList();
obj.Add(new OrderMasterChild
{
Master = i,
Childs = Child
});
}
}

Update One List of Objects Attribute with Other List using LINQ

I have a scenario as think
class a
{
String Username;
String val;
}
List<a> lst = new List<a>();
List<a> lstnew = new List<a>();
What i required is to that in lstnew i have some updated values in val Attribute (Only in Several Objects) , what i required is to update the lst with updated values in lstnew as the Username Attribute using LINQ

You can join the two lists on UserName, and then update the Values in the first list with those in the second.
For example, given this class and lists:
public class a
{
public string UserName { get; set; }
public string Value { get; set; }
}
List<a> list = new List<a>
{
new a { UserName = "Perry", Value = "A" },
new a { UserName = "Ferb", Value = "B" },
new a { UserName = "Phineas", Value = "C" }
};
List<a> newList = new List<a>
{
new a { UserName = "Phineas", Value = "X" },
new a { UserName = "Ferb", Value = "Y" },
new a { UserName = "Candace", Value = "Z" }
};
You can join to get the elements with common UserNames:
var common = from a1 in list
join a2 in newList on a1.UserName equals a2.UserName
select new { A1 = a1, A2 = a2 };
At this point, if I understand you correctly, you want to update the elements from the original list:
foreach(var c in common)
{
c.A1.Value = c.A2.Value;
}
at which point the elements in list look like:
UserName Value
-----------------
Perry A
Ferb Y
Phineas X

It sounds like you have two lists. One of which is named lst and contains a full list of usernames and a second one named lstnew that contains a list of usernames who have had their val property updated. I suggest unioning the untouched usernames with the ones that have been updated. This represents the most LINQ-friendly solution I can think of.
var updatedList = Enumerable.Union(
lst.Where(x => !lstnew.Any(y => y.Username == x.Username)),
lstnew).ToList();

you should be able to use the .Zip() method to execute this.
lst.Zip(lstNew, (orig, new) => {
orig.Username = new.Username;
return orig;
});
the idea that you are getting each pair together, then instead of returning a new one, changing the orig.Username value and return the orig.

This should also do the trick. Zip method, propsed by Alastair Pitts assumes that both collections have the same order of elements and each element from first list has correspondent element in second list. My approach is more generic, it simply looks for corresponding element by comparing Username property. Still it assumes that for each element in lstNew there is corresponding element in lst.
lstNew.ForEach(new => lst.First(orig => orig.Username == new.Username).val = new.val);

I know this is an old question but a more elegant solution that I have developed, which is a slight improvement over the one given by #JeffOgata would be:
var newList= lst.GroupJoin(lstnew ,
i => i.UserName ,
j => j.UserName ,
(i, j) => j.FirstOrDefault()?? i );
Where lst is the original list and lstnew is the new list.
This will just replace the entire object in the first list with the corresponding object in the second list (the join) if one exists.
It is a slight improvement over the answer given by #JeffOgata
The result is the same.
If you have complex objects then iterating through each object then going through all the properties was a problem, simply replacing the old object with the new one was quicker.
This hopefully will help someone.