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  • Cannot convert lamda expression

    - by Kirsty White
    If I try: Groups = students.Remove(f => f.StudentID.Equals(studentID)); I get an error on this line: f => f.StudentID.Equals(studentID) I am having difficulty from my previous posts here linq deleted users still associated with groups and here Delete method in WCF So I thought maybe I could delete the students contained within groups but I get an error Cannot convert lamda expression to type Student because it is not a delegate type.

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  • group object with equal collections

    - by Jeroen
    Hi, Suppose 2 classes, Person and Pet. Each person has a collection of 1 or more pets. How do i group the Person in to a collection where they share the same pets. Example: Person 1: Cat, Dog, Spider Person 2: Cat, Spider, Snake Person 3: Dog Person 4: Spider, Cat, Dog Person 5: Dog What i want as a result is this: Group 1: Person 1, Person 4 Group 2: Person 3, Person 5 Group 3: Person 2 How do i achieve this using LINQ?

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  • Cast IEnumerable<Inherited> To IEnumerable<Base>

    - by david2342
    I'm trying to cast an IEnumerable of an inherited type to IEnumerable of base class. Have tried following: var test = resultFromDb.Cast<BookedResource>(); return test.ToList(); But getting error: You cannot convert these types. Linq to Entities only supports conversion primitive EDM-types. The classes involved look like this: public partial class HistoryBookedResource : BookedResource { } public partial class HistoryBookedResource { public int ResourceId { get; set; } public string DateFrom { get; set; } public string TimeFrom { get; set; } public string TimeTo { get; set; } } public partial class BookedResource { public int ResourceId { get; set; } public string DateFrom { get; set; } public string TimeFrom { get; set; } public string TimeTo { get; set; } } [MetadataType(typeof(BookedResourceMetaData))] public partial class BookedResource { } public class BookedResourceMetaData { [Required(ErrorMessage = "Resource id is Required")] [Range(0, int.MaxValue, ErrorMessage = "Resource id is must be an number")] public object ResourceId { get; set; } [Required(ErrorMessage = "Date is Required")] public object DateFrom { get; set; } [Required(ErrorMessage = "Time From is Required")] public object TimeFrom { get; set; } [Required(ErrorMessage = "Time to is Required")] public object TimeTo { get; set; } } The problem I'm trying to solve is to get records from table HistoryBookedResource and have the result in an IEnumerable<BookedResource> using Entity Framework and LINQ. UPDATE: When using the following the cast seams to work but when trying to loop with a foreach the data is lost. resultFromDb.ToList() as IEnumerable<BookedResource>; UPDATE 2: Im using entity frameworks generated model, model (edmx) is created from database, edmx include classes that reprecent the database tables. In database i have a history table for old BookedResource and it can happen that the user want to look at these and to get the old data from the database entity framework uses classes with the same name as the tables to receive data from db. So i receive the data from table HistoryBookedResource in HistoryBookedResource class. Because entity framework generate the partial classes with the properties i dont know if i can make them virtual and override. Any suggestions will be greatly appreciated.

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  • Foreign Keys Duplicated in DataGridView

    - by John Doe
    I created a Windows Forms Application to which I added a DataGridView and LINQ to SQL Classes from one of my databases. I can successfully bind one of my database's tables to my DataGridView: var dataSource = from c in _db.NetworkedEquipments select c; dataGridView1.DataSource = dataSource; However, the foreign keys get duplicated, that is, the columns appear twice. How can I prevent this?

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  • How do I use a concatenation of 2 columns in a SQL DB in ASP.NET properly?

    - by user293357
    I'm using LinqToSql like this with a CheckBoxList in ASP.NET: var teachers = from x in dc.teachers select x; cbl.DataSource = teachers; cbl.DataTextField = "name"; cbl.DataValueField = "teacherID"; cbl.DataBind(); I want to display both "firstname" and "name" in the DataTextField however. I found this solution but I'm using LINQ: http://stackoverflow.com/questions/839223/concatenate-two-fields-in-a-dropdown How do I do this?

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  • Alternatives of Datatable

    - by mavera
    In my web application, I have a dynamic query that returns huge data to datatable, and this query is often recalled with different parameters. So database is exhausted. I want to get all record with no parameters to an object, and perform queries (may be with linq) on this object. So database will not be exthausted. Which objects can be used instead of datatable?

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  • How to convert a 2-d array into a dictionary object

    - by Nikron
    Hi, I have an array of type string that looks like this: "test1|True,test2|False,test3|False,test4|True". This is essentially a 2d array like so [test1][True] [test2][False] [test3][False] [test4][True]. I want to convert this into a dictionary<string,bool> using linq, something like: Dictionary<string, bool> myResults = results.Split(",".ToCharArray).ToDictionary() any ideas?

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  • Foreach loop problem for Iqueyable object

    - by Vikas
    Hi, Can we use foreach loop for Iqueryable object? I'd like to do something as follow: query = Iqueryable<Myclass> = objDataContext.Myclass; // objDataContext is an object of LINQ datacontext class int[] arr1 = new int[] { 3, 4, 5 }; foreach (int i in arr1) { query = query.Where(q => (q.f_id1 == i || q.f_id2 == i || q.f_id3 == i)); } It gives me wrong output as each time value if i is changed.

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  • How to get an array of members of an array

    - by Mystere Man
    Suppose I have a class public class Foo { public Bar { get; set; } } Then I have another class public class Gloop { public List<Foo> Foos { get; set; } } What's the easiest way to get a List of Foo.Bars? I'm using C# 4.0 and can use Linq if that is the best choice. My first thought was something like

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  • C# Check for missing number in sequence

    - by Jon
    I have an List<int> which contains 1,2,4,7,9 for example. I have a range from 0 to 10. Is there a way to determine what numbers are missing in that sequence? I thought LINQ might provide an option but I can't see one In the real world my List could contain 100,000 items so performance is key

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  • Show Detailed Error in SQL Profiler

    - by AlwaysBeCoding
    Is there any way showing the detailed exception for String or binary data would be truncated. I use LINQ to SQL and i cant figure out which column is that!? Tried numerous things but i get the same meaningless error i got from within Visual Studio. Also I use .NET 3.5 SP1, but errors are still returned useless.

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  • Using Joins vs Entity associations

    - by shivesh
    I am learning Entity framework and linq-to-entities. It's possible to get cross values from multiple tables using JOINS (join keyword) or using the navigation fields ( associations) in which case the framework knows how to reference the cross data. My question is what to use when?

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  • does @@identity return the primary key or identity field?

    - by elspiko
    Hi, My issue is that I've got update triggers on an SQL View (MS SQL 2005) which I'm mapping to LINQ to SQL entities in C#... My SQL looks correct but it complains about trying to insert a null value into a secondary table PK field. I believe my issue relates to having the primary key and identity as seperate fields in the primary table. So my question is this....when using @@identity, does it look at the primary key of the inserted row, or does it look at the field with "IDENTITY" specified???

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  • JSON.Net and Linq

    - by user1745143
    I'm a bit of a newbie when it comes to linq and I'm working on a site that parses a json feed using json.net. The problem that I'm having is that I need to be able to pull multiple fields from the json feed and use them for a foreach block. The documentation for json.net only shows how to pull just one field. I've done a few variations after checking out the linq documentation, but I've not found anything that works best. Here's what I've got so far: WebResponse objResponse; WebRequest objRequest = HttpWebRequest.Create(url); objResponse = objRequest.GetResponse(); using (StreamReader reader = new StreamReader(objResponse.GetResponseStream())) { string json = reader.ReadToEnd(); JObject rss = JObject.Parse(json); var postTitles = from p in rss["feedArray"].Children() select (string)p["item"], //These are the fields I need to also query //(string)p["title"], (string)p["message"]; //I've also tried this with console.write and labeling the field indicies for each pulled field foreach (var item in postTitles) { lbl_slides.Text += "<div class='slide'><div class='slide_inner'><div class='slide_box'><div class='slide_content'></div><!-- slide content --></div><!-- slide box --></div><div class='rotator_photo'><img src='" + item + "' alt='' /></div><!-- rotator photo --></div><!-- slide -->"; } } Has anyone seen how to pull multiple fields from a json feed and use them as part of a foreach block (or something similar?

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  • A Gentle Introduction to NuGet

    - by Joe Mayo
    Not too long ago, Microsoft released, NuGet, an automated package manager for Visual Studio.  NuGet makes it easy to download and install assemblies, and their references, into a Visual Studio project.  These assemblies, which I loosely refer to as packages, are often open source, and include projects such as LINQ to Twitter. In this post, I'll explain how to get started in using NuGet with your projects to include: installng NuGet, installing/uninstalling LINQ to Twitter via console command, and installing/uninstalling LINQ to Twitter via graphical reference menu. Installing NuGet The first step you'll need to take is to install NuGet.  Visit the NuGet site, at http://nuget.org/, click on the Install NuGet button, and download the NuGet.Tools.vsix installation file, shown below. Each browser is different (i.e. FireFox, Chrome, IE, etc), so you might see options to run right away, save to a location, or access to the file through the browser's download manager.  Regardless of how you receive the NuGet installer, execute the downloaded NuGet.Tools.vsix to install Nuget into visual Studio. The NuGet Footprint When you open visual Studio, observe that there is a new menu option on the Tools menu, titled Library Package Manager; This is where you use NuGet.  There are two menu options, from the Library Package Manager Menu that you can use: Package Manager Console and Package Manager Settings.  I won't discuss Package Manager Settings in this post, except to give you a general idea that, as one of a set of capabilities, it manages the path to the NuGet server, which is already set for you. Another menu, added by the NuGet installer, is Add Library Package Reference, found by opening the context menu for either a Solution Explorer project or a project's References folder or via the Project menu.  I'll discuss how to use this later in the post. The following discussion is concerned with the other menu option, Package Manager Console, which allows you to manage NuGet packages. Gettng a NuGet Package Selecting Tools -> Library Package Manager -> Package Manager Console opens the Package Manager Console.  As you can see, below, the Package Manager Console is text-based and you'll need to type in commands to work with packages. In this post, I'll explain how to use the Package Manager Console to install LINQ to Twitter, but there are many more commands, explained in the NuGet Package Manager Console Commands documentation.  To install LINQ to Twitter, open your current project where you want LINQ to Twitter installed, and type the following at the PM> prompt: Install-Package linqtotwitter If all works well, you'll receive a confirmation message, similar to the following, after a brief pause: Successfully installed 'linqtotwitter 2.0.20'. Successfully added 'linqtotwitter 2.0.20' to NuGetInstall. Also, observe that a reference to the LinqToTwitter.dll assembly was added to your current project. Uninstalling a NuGet Package I won't be so bold as to assume that you would only want to use LINQ to Twitter because there are other Twitter libraries available; I recommend Twitterizer if you don't care for LINQ to Twitter.  So, you might want to use the following command at the PM> prompt to remove LINQ to Twitter from your project: Uninstall-Package linqtotwitter After a brief pause, you'll see a confirmation message similar to the following: Successfully removed 'linqtotwitter 2.0.20' from NuGetInstall. Also, observe that the LinqToTwitter.dll assembly no longer appears in your project references list. Sometimes using the Package Manager Console is required for more sophisticated scenarios.  However, LINQ to Twitter doesn't have any dependencies and is a very simple install, so you can use another method of installing graphically, which I'll show you next. Graphical Installations As explained earlier, clicking Add Library Package Reference, from the context menu for either a Solution Explorer project or a project's References folder or via the Project menu opens the Add Library Package Reference window. This window will allow you to add a reference a NuGet package in your project. To the left of the window are a few accordian folders to help you find packages that are either on-line or already installed.  Just like the previous section, I'll assume you are installing LINQ to Twitter for the first time, so you would select the Online folder and click All.  After waiting for package descriptions to download, you'll notice that there are too many to scroll through in a short period of time, over 900 as I write this.  Therefore, use the search box located at the top right corner of the window and type LINQ to Twitter as I've done in the previous figure. You'll see LINQ to Twitter appear in the list. Click the Install button on the LINQ to Twitter entry. If the installation was successful, you'll see a message box display and disappear quickly (or maybe not if your machine is very fast or you blink at that moment). Then you'll see a reference to the LinqToTwitter.dll assembly in your project's references list. Note: While running this demo, I ran into an issue where VS had created a file lock on an installation folder without releasing it, causing an error with "packagename already exists. Skipping..." and then an error describing that it couldn't write to a destination folder.  I resolved the problem by closing and reopening VS. If you open the Add a Library Package Reference window again, you'll see LINQ to Twitter listed in the Recent packages folder. Summary You can install NuGet via the on-line home page with a click of a button.  Nuget provides two ways to work with packages, via console or graphical window.  While the graphical window is easiest, the console window is more powerful. You can now quickly add project references to many available packages via the NuGet service. Joe

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  • Can this be done using LINQ/Lambda, C#3.0

    - by Newbie
    Objective: Generate dates based on Week Numbers Input: StartDate, WeekNumber Output: List of dates from the Week number specified till the StartDate i.e. If startdate is 23rd April, 2010 and the week number is 1, then the program should return the dates from 16th April, 2010 till the startddate. The function public List<DateTime> GetDates(DateTime startDate,int weeks) { List<DateTime> dt = new List<DateTime>(); int days = weeks * 7; DateTime endDate = startDate.AddDays(-days); TimeSpan ts = startDate.Subtract(endDate); for (int i = 0; i <= ts.Days; i++) { DateTime dt1 = endDate.AddDays(i); dt.Add(dt1); } return dt; } I am calling this function as DateTime StartDate = DateTime.ParseExact("20100423", "yyyyMMdd", System.Globalization.CultureInfo.InvariantCulture); List<DateTime> dtList = GetDates(StartDate, 1); The program is working fine. Question is using C# 3.0 feature like Linq, Lambda etc. can I rewrite the program. Why? Because I am learning linq and lambda and want to implement the same. But as of now the knowledge is not sufficient to do the same by myself. Thanks.

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  • Add objects to Arraylist inside loop and get a list of them outside loops

    - by AgusDG
    Im already done with a method to do a shot on a board (bidimensional array). THe shot goes from the bottom to the top, and depending of the direction, it do bounces on the walls to get to the top. The thing is that I did the method to represent the trayectory with an 'x'. Now, I want to add the coordinates x and y of each position of the shot (b [x][y]) to and Arraylist of Objects Position. public Position(int row,int col) { this.row = row; this.col = col; } The thing is that the method uses a for loop and inside if loops, and I'll need to create the objects inside, and get them outside. I did that : public static ArrayList<Position> showTrayectory (char [][] b , int shotDirection, char bubble){ int row = 0, col = 0; ArrayList<Position> aListPos = new ArrayList<Position>(); Position positionsOfShot = new Position(row,col); START = ((RIGHT_WALL)/2) + shotDirection; boolean shotRight = false; if(shotDirection < 0) shotRight = false; else if(shotDirection > 0) shotRight = true; for(int y = BOTTOM,x = START ;y >= 0;y--) { if(!isOut(y,x) && !emptyCell(y,x)) break; if(x <= LEFT_WALL) shotRight = true; if(x >= RIGHT_WALL) shotRight = false; if(!isOut(y,x) && shotRight == true) { positionsOfShot = new Position(y,x); aListPos.add(positionsOfShot); b[y][x] = SHOT; ++x; } if(!isOut(y,x) && shotRight == false){ positionsOfShot = new Position(y,x); aListPos.add(positionsOfShot); b[y][x] = SHOT; --x; } } // The nested for loops below are for showing the positions // But I dont need it that way // I must get the trayectory from an ArrayList and print it from there for(int y=0;y < b.length;y++){ System.out.println(); for(int x=0;x < b[y].length;x++){ System.out.print(" "+b [y][x]+" "); } } System.out.println("\nTrayectory of the shot ["+shotDirection+"]"); System.out.println("Next bubble ["+bubble+"]"); for( Position ii : aListPos){ System.out.println("(" + positionsOfShot.getFila() + "," + positionsOfShot.getColumna()+")"); } return aListPos; } The sentence " b[y][x] = SHOT; " is still there, to see the proper trayectory of the shot (its not needed that way), but what I need, is getting the trayectory in an ArrayList, and print the trayectory from there. All that I get is a wrong position, and repeated during the number of positions the shot goes through. I need some help. I suppose the problem is that Im creating and adding Position Objects inside an ArrayList inside loops, but in a wrong way. I will need you to explain me how to do it properly ; ) Thanks in advance. I'll add the output for you see better what is that above haha *************************** y b y b g r b g o y g a a r y o y y r b y g r r o b o y y g b a r y r o a y y o o r r g r - - - x - - - - - - - - - x - - - - - - - - - x - - - - - - - - - x - - - - - - - - - x - - - - - - - - - x - - - - - - - x - - - - - - - x - - - - - - - x - - - Trayectory of the shot [1] Next bubble [y] (5,3) (5,3) (5,3) (5,3) (5,3) (5,3) (5,3) (5,3) (5,3) Action?

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  • Using Comparable to compare objects and sorting them in a TreeMap

    - by arjacsoh
    II cannot understand how should the natural ordering of class be "consistent with equals" when implementing the Comparable interface. I deteted a flaw in my program and therefore I deteced that in the documentantion of the interface Comparable. My problem is that although two Objects are considered as distinct on the base of equals method, the TreeMap structure treats them as equal and consequently does not accept the second insert. The sample code is: public class Car implements Comparable<Car> { int weight; String name; public Car(int w, String n) { weight=w; name=n; } public boolean equals(Object o){ if(o instanceof Car){ Car d = (Car)o; return ((d.name.equals(name)) && (d.weight==weight)); } return false; } public int hashCode(){ return weight/2 + 17; } public String toString(){ return "I am " +name+ " !!!"; } public int compareTo(Car d){ if(this.weight>d.weight) return 1; else if(this.weight<d.weight) return -1; else return 0; } /*public int compareTo(Car d){ return this.name.compareTo(d.name); }*/ } public static void main(String[] args) { Car d1 = new Car(100, "a"); Car d2 = new Car(110, "b"); Car d3 = new Car(110, "c"); Car d4 = new Car(100, "a"); Map<Car, Integer> m = new HashMap<Car, Integer>(); m.put(d1, 1); m.put(d2, 2); m.put(d3, 3); m.put(d4, 16); for(Map.Entry<Car, Integer> me : m.entrySet()) System.out.println(me.getKey().toString() + " " +me.getValue()); TreeMap<Car, Integer> tm = new TreeMap<Car, Integer>(m); System.out.println("After Sorting: "); for(Map.Entry<Car, Integer> me : tm.entrySet()) System.out.println(me.getKey().toString() + " " +me.getValue()); } The output is : I am a !!! 16 I am c !!! 3 I am b !!! 2 After Sorting: I am a !!! 16 I am c !!! 2 That is, that the object c has replaced (somewhat) object b. If I comment the original equals method and uncomment the second equals method, which compares the objects according name, the output is the expected: I am a !!! 16 I am c !!! 3 I am b !!! 2 After Sorting: I am a !!! 16 I am b !!! 2 I am c !!! 3 Why does it come around in this way and what should I alter in order to insert and sort different objects with some attributes of equal value in a TreeMap?

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