var menuQuery = repository.MenuMasters.OrderBy(c => c.Position).Select(c => new { ID = c.MenuMasterID, Position = (MenuItemPosition)c.Position + " - " + c.SitePage.Title });
ViewBag.ParentID = new SelectList(menuQuery, "ID", "Position", selectedParentId);
public int Position { get; set; }
public MenuItemPosition MenuPosition {
get { return (MenuItemPosition)Position; }
set { Position = (int)value; }
}
public enum MenuItemPosition {
Top = 1, Main = 2, Footer = 3
}
I got an error which said "Unable to cast the type 'Type Name' to type 'Type Name'. LINQ to Entities only supports casting Entity Data Model primitive types."
MenuItemPosition is "Enum", Title is "string"
How can I fix this? Many thanks~!
I think you need to add .ToList after OrderBy, as string concatenation is not supported with Linq to Entities.. So your query will look something like :
var menuQuery = repository.MenuMasters.OrderBy(c => c.Position).ToList().Select(c => new { ID = c.MenuMasterID, Position = ((MenuItemPosition)c.Position).convertToString() + " - " + c.SitePage.Title });
Try something like
var menuQuery = repository.MenuMasters.OrderBy(c => c.Position).Select(c => new { ID = c.MenuMasterID, Position = c.Position.ToString() + " - " + c.SitePage.Title });
Related
I have list of objects as described below:
List<Maths> mObjs = new List<Maths>();
mObjs.Add(new Maths{ Name = "Jack", M1 = 10, M2 = 5, M3 = 0, M4 = 2, M5 =1 });
mObjs.Add(new Maths { Name = "Jill", M1 = 2, M2 = 3, M3 = 4, M4 = 1, M5 = 0 });
mObjs.Add(new Maths { Name = "Michel", M1 = 12, M2 = 15, M3 = 10, M4 = 12, M5 = 11 });
Now I need to calculated the total aggregated value for all three people.
I need to get the below results, probably a new other class
List<Results> mRes = new List<Results>();
public class Results{
public string Name { get; set; }
public int TotalValue { get; set; }
}
mRes.Name = "M1"
mRes.TotalValue = 24;
mRes.Name = "M2"
mRes.TotalValue = 23;
mRes.Name = "M3"
mRes.TotalValue = 14;
mRes.Name = "M4"
mRes.TotalValue = 15;
mRes.Name = "M5"
mRes.TotalValue = 12;
How can I get this data from mObjs using linq query? I know we can do it using for, but want to know if there are any better ways to get this using linq query because that reduces lines of code and I have similar requirements in many other places and dont want to write number of foreach or fors every time.
You can use a pre selection list to list both the name and the field to select
var lookups = new Dictionary<string,Func<Maths,int>> {
{"M1", x => x.M1 },
{"M2", x => x.M2 },
{"M3", x => x.M3 },
{"M4", x => x.M4 },
{"M5", x => x.M5 },
};
Then you can simply do
var mRes = dlookups.Select(x => new Results {
Name= x.Key,
TotalValue = mObjs.Sum(x.Value)
}).ToList();
BEGIN UPDATED*
In response to comments
The lambda expression is just a function from your source class to an int.
For example
class Sub1 {
string M3 {get;set;}
int M4 {get;set;}
}
class Math2 {
string Name {get;set;}
string M1 {get;set;}
string M2 {get;set;}
Sub1 Sub {get;set;}
}
var lookups = new Dictionary<string,Func<Math2,int>> {
{ "M1", x => int.Parse(x.M1) },
{ "M2", x => int.Parse(x.M2) },
{ "M3", x => int.Parse(x.Sub.M3) },
{ "M4", x => int.Parse(x.Sub.M4} }
};
Or if you want to put a little error checking in, you can either use functions or embed the code.
int GetInt(string source) {
if (source == null) return 0;
int result;
return int.TryParse(source, out result) ? result : 0;
}
var lookups = new Dictionary<string,Func<Math2,int>> {
{ "M1", x => {
int result;
return x == null ? 0 : (int.TryParse(x,out result) ? result : 0);
},
{ "M2", x => GetInt(x) },
{ "M3", x => x.Sub == null ? 0 : GetInt(x.Sub.M3) },
{ "M4", x => x.Sub == null ? 0 : x.Sub.M4}
};
END UPDATED
If you want to go further you could use reflection to build the lookups dictionary.
Here is a helper function that will generate the lookups for all Integer properties of a class.
public Dictionary<string,Func<T,int>> GenerateLookups<T>() where T: class {
// This just looks for int properties, you could add your own filter
var properties = typeof(T).GetProperties().Where(pi => pi.PropertyType == typeof(int));
var parameter = Expression.Parameter(typeof(T));
return properties.Select(x => new {
Key = x.Name,
Value = Expression.Lambda<Func<T,int>>(Expression.Property(parameter,x),parameter).Compile()
}).ToDictionary (x => x.Key, x => x.Value);
}
Now you can just do:
var mRes=GenerateLookups<Maths>().Select( x => new Results
{
Name = x.Key,
TotalValue = mObjs.Sum(x.Value)
}).ToList();
Not very smart but efficient and readable:
int m1Total= 0;
int m2Total= 0;
int m3Total= 0;
int m4Total= 0;
int m5Total= 0;
foreach(Maths m in mObjs)
{
m1Total += m.M1;
m2Total += m.M2;
m3Total += m.M3;
m4Total += m.M4;
m5Total += m.M5;
}
List<Results> mRes = new List<Results>
{
new Results{ Name = "M1", TotalValue = m1Total },
new Results{ Name = "M2", TotalValue = m2Total },
new Results{ Name = "M3", TotalValue = m3Total },
new Results{ Name = "M4", TotalValue = m4Total },
new Results{ Name = "M5", TotalValue = m5Total },
};
Result:
Name: "M1" TotalValue: 24
Name: "M2" TotalValue: 23
Name: "M3" TotalValue: 14
Name: "M4" TotalValue: 15
Name: "M5" TotalValue: 12
Edit: since you've explicitly asked for LINQ, if the properties are always these five i don't see why you need to use LINQ at all. If the number can change i would use a different structure.
You could for example use
a single List<Measurement> instead of multiple properties where Measurement is another class that stores the name and the value or you could use
a Dictionary<string, int> for efficient lookup.
You can try out some thing like this :
mRes.Add(new Results() { Name = "M1", TotalValue = mObjs.Sum(x => x.M1) });
To programmatically iterate through all the class properties, you might need to employ reflection.
I was trying to implement the jQgrid using MvcjQgrid and i got this exception.
System.NotSupportedException was unhandled by user code
Message=The method 'Skip' is only supported for sorted input in LINQ to Entities. The method 'OrderBy' must be called before the method 'Skip'.
Though OrdeyBy is used before Skip method why it is generating the exception? How can it be solved?
I encountered the exception in the controller:
public ActionResult GridDataBasic(GridSettings gridSettings)
{
var jobdescription = sm.GetJobDescription(gridSettings);
var totalJobDescription = sm.CountJobDescription(gridSettings);
var jsonData = new
{
total = totalJobDescription / gridSettings.PageSize + 1,
page = gridSettings.PageIndex,
records = totalJobDescription,
rows = (
from j in jobdescription
select new
{
id = j.JobDescriptionID,
cell = new[]
{
j.JobDescriptionID.ToString(),
j.JobTitle,
j.JobType.JobTypeName,
j.JobPriority.JobPriorityName,
j.JobType.Rate.ToString(),
j.CreationDate.ToShortDateString(),
j.JobDeadline.ToShortDateString(),
}
}).ToArray()
};
return Json(jsonData, JsonRequestBehavior.AllowGet);
}
GetJobDescription Method and CountJobDescription Method
public int CountJobDescription(GridSettings gridSettings)
{
var jobdescription = _dataContext.JobDescriptions.AsQueryable();
if (gridSettings.IsSearch)
{
jobdescription = gridSettings.Where.rules.Aggregate(jobdescription, FilterJobDescription);
}
return jobdescription.Count();
}
public IQueryable<JobDescription> GetJobDescription(GridSettings gridSettings)
{
var jobdescription = orderJobDescription(_dataContext.JobDescriptions.AsQueryable(), gridSettings.SortColumn, gridSettings.SortOrder);
if (gridSettings.IsSearch)
{
jobdescription = gridSettings.Where.rules.Aggregate(jobdescription, FilterJobDescription);
}
return jobdescription.Skip((gridSettings.PageIndex - 1) * gridSettings.PageSize).Take(gridSettings.PageSize);
}
And Finally FilterJobDescription and OrderJobDescription
private static IQueryable<JobDescription> FilterJobDescription(IQueryable<JobDescription> jobdescriptions, Rule rule)
{
if (rule.field == "JobDescriptionID")
{
int result;
if (!int.TryParse(rule.data, out result))
return jobdescriptions;
return jobdescriptions.Where(j => j.JobDescriptionID == Convert.ToInt32(rule.data));
}
// Similar Statements
return jobdescriptions;
}
private IQueryable<JobDescription> orderJobDescription(IQueryable<JobDescription> jobdescriptions, string sortColumn, string sortOrder)
{
if (sortColumn == "JobDescriptionID")
return (sortOrder == "desc") ? jobdescriptions.OrderByDescending(j => j.JobDescriptionID) : jobdescriptions.OrderBy(j => j.JobDescriptionID);
return jobdescriptions;
}
The exception means that you always need a sorted input if you apply Skip, also in the case that the user doesn't click on a column to sort by. I could imagine that no sort column is specified when you open the grid view for the first time before the user can even click on a column header. To catch this case I would suggest to define some default sorting that you want when no other sorting criterion is given, for example:
switch (sortColumn)
{
case "JobDescriptionID":
return (sortOrder == "desc")
? jobdescriptions.OrderByDescending(j => j.JobDescriptionID)
: jobdescriptions.OrderBy(j => j.JobDescriptionID);
case "JobDescriptionTitle":
return (sortOrder == "desc")
? jobdescriptions.OrderByDescending(j => j.JobDescriptionTitle)
: jobdescriptions.OrderBy(j => j.JobDescriptionTitle);
// etc.
default:
return jobdescriptions.OrderBy(j => j.JobDescriptionID);
}
Edit
About your follow-up problems according to your comment: You cannot use ToString() in a LINQ to Entities query. And the next problem would be that you cannot create a string array in a query. I would suggest to load the data from the DB with their native types and then convert afterwards to strings (and to the string array) in memory:
rows = (from j in jobdescription
select new
{
JobDescriptionID = j.JobDescriptionID,
JobTitle = j.JobTitle,
JobTypeName = j.JobType.JobTypeName,
JobPriorityName = j.JobPriority.JobPriorityName,
Rate = j.JobType.Rate,
CreationDate = j.CreationDate,
JobDeadline = j.JobDeadline
})
.AsEnumerable() // DB query runs here, the rest is in memory
.Select(a => new
{
id = a.JobDescriptionID,
cell = new[]
{
a.JobDescriptionID.ToString(),
a.JobTitle,
a.JobTypeName,
a.JobPriorityName,
a.Rate.ToString(),
a.CreationDate.ToShortDateString(),
a.JobDeadline.ToShortDateString()
}
})
.ToArray()
I had the same type of problem after sorting using some code from Adam Anderson that accepted a generic sort string in OrderBy.
After getting this excpetion, i did lots of research and found that very clever fix:
var query = SelectOrders(companyNo, sortExpression);
return Queryable.Skip(query, iStartRow).Take(iPageSize).ToList();
Hope that helps !
SP
I'm using MVC3 ajaxgrid scaffolding with EF4.1 code first and i've this error:
Cannot implicitly convert type 'System.Linq.IQueryable' to 'System.Data.Objects.ObjectQuery'
The code with the error in, is autogenerated:
public ActionResult GridData(int start = 0, int itemsPerPage = 20, string orderBy = "UserID", bool desc = false)
{
Response.AppendHeader("X-Total-Row-Count", repository.Users.Count().ToString());
ObjectQuery<User> users = (repository as IObjectContextAdapter).ObjectContext.CreateObjectSet<User>();
users = repository.Users.Include(u => u.Role); //ERROR HERE
users = users.OrderBy("it." + orderBy + (desc ? " desc" : ""));
return PartialView(users.Skip(start).Take(itemsPerPage));
}
This is the Users repository method and the Roles Foreign Key
public IQueryable<Entities.User> Users
{
get { return context.Users; }
}
public IQueryable<Entities.Role>Roles
{
get { return context.Roles; }
}
How can i resolve the conversion?
Get rid of the Lambda and use the related object:
var users = repository.Users.Include("Role"); //ERROR HERE
Assuming the entity User has a navigational property Role.
The reason is clear:
You have users variable with ObjectQuery<User> type then you assign that variable result of a query which is IQueryable<User>.
UPDATE:
Try the code below:
public ActionResult GridData(int start = 0, int itemsPerPage = 20, string orderBy = "UserID", bool desc = false)
{
Response.AppendHeader("X-Total-Row-Count", repository.Users.Count().ToString());
//ObjectQuery<User> users = (repository as IObjectContextAdapter).ObjectContext.CreateObjectSet<User>();
var users = repository.Users.Include(u => u.Role); //ERROR HERE
users = users.OrderBy("it." + orderBy + (desc ? " desc" : ""));
return PartialView(users.Skip(start).Take(itemsPerPage));
}
.NET 4, I have
public class Humi
{
public int huKey { get; set; }
public string huVal { get; set; }
}
And in another class is this code in a method:
IEnumerable<Humi> someHumi = new List<Humi>(); //This is actually ISingleResult that comes from a LinqToSql-fronted sproc but I don't think is relevant for my question
var humia = new Humi { huKey = 1 , huVal = "a"};
var humib = new Humi { huKey = 1 , huVal = "b" };
var humic = new Humi { huKey = 2 , huVal = "c" };
var humid = new Humi { huKey = 2 , huVal = "d" };
I want to create a single IDictionary <int,string[]>
with key 1 containing ["a","b"] and key 2 containing ["c","d"]
Can anyone point out a decent way to to that conversion with Linq?
Thanks.
var myDict = someHumi
.GroupBy(h => h.huKey)
.ToDictionary(
g => g.Key,
g => g.ToArray())
Create an IEnumerable<IGrouping<int, Humi>> and then project that into a dictionary. Note .ToDictionary returns a Dictionary, not an IDictionary.
You can use ToLookup() which allows each key to hold multiple values, exactly your scenario (note that each key would hold an IEnumerable<string> of values though not an array):
var myLookup = someHumi.ToLookup(x => x.huKey, x => x.huVal);
foreach (var item in myLookup)
{
Console.WriteLine("{0} contains: {1}", item.Key, string.Join(",", item));
}
Output:
1 contains: a,b
2 contains: c,d
I'm trying to write a LINQ query and am having problems. I'm not sure if lambda expressions are the answer or not but I think they may be.
I have two combo boxes on my form: "State" and "Color".
I want to select Widgets from my database based on the values of these two dropdowns.
My widgets can be in one of the following states: Not Started, In Production, In Finishing, In Inventory, Sold. Widgets can have any color in the 'color' table in the database.
The 'state' combobox has selections "Not Sold," "In Production/Finishing", "Not Started," "In Production," "In Finishing," "In Inventory," "Sold." (I hope these are self-explanatory.)
The 'color' dropdown has "All Colors," and a separate item for each color in the database.
How can I create a LINQ query to select the widgets I want from the database based on the dropdowns?
var WidgetStateChoosen = "Sold";
//var WidgetStateChoosen = "All Widgets";
var WidgetColourChoosen = "Orange";
//var WidgetColourChoosen = "All Colours";
var widgetselected = Widgets.Where
(w =>
( (WidgetStateChoosen == "All Widgets") ? (w.WidgetState != WidgetStateChoosen) : (w.WidgetState == WidgetStateChoosen) )
&&
( (WidgetColourChoosen == "All Colours") ? (w.WidgetColour != WidgetColourChoosen) : (w.WidgetColour == WidgetColourChoosen) )
);
Way more code then I wish, but oh well! I wasnt sure I completely understood your state and selectionstate, but I hope my example is still helpful.
[TestMethod]
public void SelectionTest()
{
var userSelections = GetUserSelections("AllColor", (SelectedState[])Enum.GetValues(typeof(SelectedState)));
var inventory = this.GetInventory();
foreach (var currentSelection in userSelections)
{
var selection = currentSelection;
var result = from item in inventory
where (item.Color == selection.Color || selection.Color == "AllColor") &&
this.GetStates(selection.State).Contains(item.State)
select item;
Console.WriteLine("Item selected for selection: Color:{0} SelectedState:{1}", selection.Color, selection.State);
foreach (var item in result)
{
Console.WriteLine("Item Color:{0};Item State:{1}", item.Color, item.State);
}
Console.WriteLine("");
}
}
private IEnumerable<State> GetStates(SelectedState state)
{
var list = new List<State>();
foreach (State currentState in Enum.GetValues(typeof(State)))
{
if (((int)currentState & (int)state) == (int)currentState)
{
list.Add(currentState);
}
}
return list;
}
private IEnumerable<Item> GetInventory()
{
return new List<Item>()
{
new Item() {State = State.NotStarted, Color = "Blue"},
new Item() {State = State.InFinishing, Color = "Red"},
new Item() {State = State.Sold, Color = "Yellow"},
new Item() {State = State.Sold, Color = "Blue"},
new Item() {State = State.InProduction, Color = "Blue"},
new Item() {State = State.InInventory, Color = "Blue"},
};
}
private IEnumerable<UserSelection> GetUserSelections(String color, IEnumerable<SelectedState> states)
{
var list = new List<UserSelection>();
foreach (var state in states)
{
list.Add(new UserSelection() { Color = color, State = state });
}
return list;
}
[Flags]
private enum State
{
NotStarted = 1,
InProduction = 2,
InFinishing = 4,
InInventory = 8,
Sold = 16
}
private enum SelectedState
{
NotSold = State.InInventory, //Where does it map? I assume INInventory even if it doesnt make much sense
InProductionOrFinishing = State.InProduction | State.InFinishing,
NotStarted = State.NotStarted,
InProduction = State.InProduction,
InFinishing = State.InFinishing,
InInventory = State.InInventory,
Sold = State.Sold,
SomeBizarroTrippleState = State.InProduction | State.Sold | State.NotStarted
}
private class UserSelection
{
public String Color { get; set; }
public SelectedState State { get; set; }
}
private class Item
{
public String Color { get; set; }
public State State { get; set; }
}
var query = db.Widgets;
if (stateFilter == "Not sold")
query = query.Where(w => w.State != WidgetState.Sold);
else if (stateFilter == "In Production/Finishing")
query = query.Where(w => w.State == WidgetState.InProduction || w.State == WidgetState.Finishing);
if (colorFilter != "All colors")
query = query.Where(w => w.Color = colorFilter);
(of course you should have a better way of testing the selected value from the combobox, testing on strings is really bad...)