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  • C#, LINQ. How to find an element within group of elements

    - by Bobb
    Imagine you have int[] data = new int [] { 1, 2, 1, 1, 3, 2 } I need sub-array with only those which conform to a condition data[i] data[i-1] && data[i] data[i + 1]... i.e. I need all items which stick over their immediate neighbours. From example above I should get { 2, 3 } Can it be done in LINQ? Thanks

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  • What is the difference between Equals and = in LINQ?

    - by sunpech
    What is the difference between Equals and = in LINQ? Dim list As List(Of Foo) = (From a As Foo In FooList _ Join b As Bar In BarList _ On a.Something = b.Something _ Select a).ToList() versus Dim list As List(Of Foo) = (From a As Foo In FooList _ Join b As Bar In BarList _ On a.Something Equals b.Something _ Select a).ToList()

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  • How to convert SQL Statement with TOP, COUNT and GROUP BY to return an object list with LINQ

    - by Junior Mayhé
    Hello guys does anyone know how to convert this SQL statement to a LINQ to a List? SELECT TOP(5) COUNT(CategoryId), CategoryName FROM Tickets GROUP BY CategoryName The result would be something like public static List<Categories> List() { MyEntities db = new MyEntities(); /* here it should return a list o Category type */; return db.Category.GroupBy(...).OrderBy(...); }

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  • How to check results of LINQ to SQL query?

    - by rem
    In a WPF app I'd like to check if a return of a LINQ to SQL query contains some records, but my approach doesn't work: TdbDataContext context = new TdbDataContext(); var sh = from p in context.Items where p.Selected == true select p; if (sh == null) { MessageBox.Show("There are no Selected Items"); } Where am I wrong?

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  • How to select with Linq to Entity from one table with two different variables?

    - by George
    I have a table where I have items under two different types as you can see below: How can I select from this table with Linq to Entity to get the result with two variables? where ItemType = Type1 and ItemType == Type2 .... select new {typeOne == "", typeTwo == ""}; ID ItemName ItemType 1 ItemOne Type1 2 ItemTwo Type1 3 ItemThree Type1 4 ItemFour Type1 5 ItemTFive Type2 6 ItemSix Type2 7 ItemSeven Type2 8 ItemEight Type2

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  • 30 seconds from File|New to a new CRUD Silverlight application with Teleriks new LINQ Implementation

    Last month Telerik released its new LINQ implementation and last week we released the new Data Services Wizard for Telerik OpenAccess, which supports both traditional OpenAccess entities and the new LINQ implementation. I will a walk you through the process where you can connect to a database, add a new domain model, wrap it in a new WCF Data Services (Astoria) service, and add a CRUD enabled Silverlight application. All in 30 seconds! Step 1: Build your Domain Model (20 seconds) Open Visual Studio 2010 RTM (or 2008) and add a new ASP.NET project. Right click on the project and select Add|New Item and choose Telerk OpenAccess Domain Model from the item template list. The Visual Entity Designer wizard comes up. Select the database server you are using in the first screen (SQL Server, Oracle, SQL Azure, MySQL, etc) and then also build your database connection string. Next select the tables, views, and stored procedures you want ...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Working with Timelines with LINQ to Twitter

    - by Joe Mayo
    When first working with the Twitter API, I thought that using SinceID would be an effective way to page through timelines. In practice it doesn’t work well for various reasons. To explain why, Twitter published an excellent document that is a must-read for anyone working with timelines: Twitter Documentation: Working with Timelines This post shows how to implement the recommended strategies in that document by using LINQ to Twitter. You should read the document in it’s entirety before moving on because my explanation will start at the bottom and work back up to the top in relation to the Twitter document. What follows is an explanation of SinceID, MaxID, and how they come together to help you efficiently work with Twitter timelines. The Role of SinceID Specifying SinceID says to Twitter, “Don’t return tweets earlier than this”. What you want to do is store this value after every timeline query set so that it can be reused on the next set of queries.  The next section will explain what I mean by query set, but a quick explanation is that it’s a loop that gets all new tweets. The SinceID is a backstop to avoid retrieving tweets that you already have. Here’s some initialization code that includes a variable named sinceID that will be used to populate the SinceID property in subsequent queries: // last tweet processed on previous query set ulong sinceID = 210024053698867204; ulong maxID; const int Count = 10; var statusList = new List<status>(); Here, I’ve hard-coded the sinceID variable, but this is where you would initialize sinceID from whatever storage you choose (i.e. a database). The first time you ever run this code, you won’t have a value from a previous query set. Initially setting it to 0 might sound like a good idea, but what if you’re querying a timeline with lots of tweets? Because of the number of tweets and rate limits, your query set might take a very long time to run. A caveat might be that Twitter won’t return an entire timeline back to Tweet #0, but rather only go back a certain period of time, the limits of which are documented for individual Twitter timeline API resources. So, to initialize SinceID at too low of a number can result in a lot of initial tweets, yet there is a limit to how far you can go back. What you’re trying to accomplish in your application should guide you in how to initially set SinceID. I have more to say about SinceID later in this post. The other variables initialized above include the declaration for MaxID, Count, and statusList. The statusList variable is a holder for all the timeline tweets collected during this query set. You can set Count to any value you want as the largest number of tweets to retrieve, as defined by individual Twitter timeline API resources. To effectively page results, you’ll use the maxID variable to set the MaxID property in queries, which I’ll discuss next. Initializing MaxID On your first query of a query set, MaxID will be whatever the most recent tweet is that you get back. Further, you don’t know what MaxID is until after the initial query. The technique used in this post is to do an initial query and then use the results to figure out what the next MaxID will be.  Here’s the code for the initial query: var userStatusResponse = (from tweet in twitterCtx.Status where tweet.Type == StatusType.User && tweet.ScreenName == "JoeMayo" && tweet.SinceID == sinceID && tweet.Count == Count select tweet) .ToList(); statusList.AddRange(userStatusResponse); // first tweet processed on current query maxID = userStatusResponse.Min( status => ulong.Parse(status.StatusID)) - 1; The query above sets both SinceID and Count properties. As explained earlier, Count is the largest number of tweets to return, but the number can be less. A couple reasons why the number of tweets that are returned could be less than Count include the fact that the user, specified by ScreenName, might not have tweeted Count times yet or might not have tweeted at least Count times within the maximum number of tweets that can be returned by the Twitter timeline API resource. Another reason could be because there aren’t Count tweets between now and the tweet ID specified by sinceID. Setting SinceID constrains the results to only those tweets that occurred after the specified Tweet ID, assigned via the sinceID variable in the query above. The statusList is an accumulator of all tweets receive during this query set. To simplify the code, I left out some logic to check whether there were no tweets returned. If  the query above doesn’t return any tweets, you’ll receive an exception when trying to perform operations on an empty list. Yeah, I cheated again. Besides querying initial tweets, what’s important about this code is the final line that sets maxID. It retrieves the lowest numbered status ID in the results. Since the lowest numbered status ID is for a tweet we already have, the code decrements the result by one to keep from asking for that tweet again. Remember, SinceID is not inclusive, but MaxID is. The maxID variable is now set to the highest possible tweet ID that can be returned in the next query. The next section explains how to use MaxID to help get the remaining tweets in the query set. Retrieving Remaining Tweets Earlier in this post, I defined a term that I called a query set. Essentially, this is a group of requests to Twitter that you perform to get all new tweets. A single query might not be enough to get all new tweets, so you’ll have to start at the top of the list that Twitter returns and keep making requests until you have all new tweets. The previous section showed the first query of the query set. The code below is a loop that completes the query set: do { // now add sinceID and maxID userStatusResponse = (from tweet in twitterCtx.Status where tweet.Type == StatusType.User && tweet.ScreenName == "JoeMayo" && tweet.Count == Count && tweet.SinceID == sinceID && tweet.MaxID == maxID select tweet) .ToList(); if (userStatusResponse.Count > 0) { // first tweet processed on current query maxID = userStatusResponse.Min( status => ulong.Parse(status.StatusID)) - 1; statusList.AddRange(userStatusResponse); } } while (userStatusResponse.Count != 0 && statusList.Count < 30); Here we have another query, but this time it includes the MaxID property. The SinceID property prevents reading tweets that we’ve already read and Count specifies the largest number of tweets to return. Earlier, I mentioned how it was important to check how many tweets were returned because failing to do so will result in an exception when subsequent code runs on an empty list. The code above protects against this problem by only working with the results if Twitter actually returns tweets. Reasons why there wouldn’t be results include: if the first query got all the new tweets there wouldn’t be more to get and there might not have been any new tweets between the SinceID and MaxID settings of the most recent query. The code for loading the returned tweets into statusList and getting the maxID are the same as previously explained. The important point here is that MaxID is being reset, not SinceID. As explained in the Twitter documentation, paging occurs from the newest tweets to oldest, so setting MaxID lets us move from the most recent tweets down to the oldest as specified by SinceID. The two loop conditions cause the loop to continue as long as tweets are being read or a max number of tweets have been read.  Logically, you want to stop reading when you’ve read all the tweets and that’s indicated by the fact that the most recent query did not return results. I put the check to stop after 30 tweets are reached to keep the demo from running too long – in the console the response scrolls past available buffer and I wanted you to be able to see the complete output. Yet, there’s another point to be made about constraining the number of items you return at one time. The Twitter API has rate limits and making too many queries per minute will result in an error from twitter that LINQ to Twitter raises as an exception. To use the API properly, you’ll have to ensure you don’t exceed this threshold. Looking at the statusList.Count as done above is rather primitive, but you can implement your own logic to properly manage your rate limit. Yeah, I cheated again. Summary Now you know how to use LINQ to Twitter to work with Twitter timelines. After reading this post, you have a better idea of the role of SinceID - the oldest tweet already received. You also know that MaxID is the largest tweet ID to retrieve in a query. Together, these settings allow you to page through results via one or more queries. You also understand what factors affect the number of tweets returned and considerations for potential error handling logic. The full example of the code for this post is included in the downloadable source code for LINQ to Twitter.   @JoeMayo

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  • [LINQ] Master &ndash; Detail Same Record(II)

    - by JTorrecilla
    In my previous post, I introduced my problem, but I didn’t explain the problem with Entity Framework When you try the solution indicated you will take the following error: LINQ to Entities don’t recognize the method 'System.String Join(System.String, System.Collections.Generic.IEnumerable`1[System.String])’ of the method, and this method can’t be translated into a stored expression. The query that produces that error was: 1: var consulta = (from TCabecera cab in 2: contexto_local.TCabecera 3: let Detalle = (from TDetalle detalle 4: in cab.TDetalle 5: select detalle.Nombre) 6: let Nombres = string.Join(",",Detalle ) 7: select new 8: { 9: cab.Campo1, 10: cab.Campo2, 11: Nombres 12: }).ToList(); 13: grid.DataSource=consulta;   Why is this error happening? This error happens when the query couldn’t be translated into T-SQL. Solutions? To quit that error, we need to execute the query on 2 steps: 1: var consulta = (from TCabecera cab in 2: contexto_local.TCabecera 3: let Detalle = (from TDetalle detalle 4: in cab.TDetalle 5: select detalle.Nombre) 6: select new 7: { 8: cab.Campo1, 9: cab.Campo2, 10: Detalle 11: }).ToList(); 12: var consulta2 = (from dato in consulta 13: let Nombes = string.Join(",",dato.Detalle) 14: select new 15: { 16: dato.Campo1, 17: dato.Campo2, 18: Nombres 19: }; 20: grid.DataSource=consulta2.ToList(); Curiously This problem happens with Entity Framework but, the same problem can’t be reproduced on LINQTo – SQL, that it works fine in one unique step. Hope It’s helpful Best Regards

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  • [LINQ] Master&ndash;Detail Same Record (I)

    - by JTorrecilla
    PROBLEM Firstly, I am working on a project based on LINQ, EF, and C# with VS2010. The following Table shows what I have and what I want to show. Header C1 C2 C3 1 P1 01/01/2011 2 P2 01/02/2011 Details 1 1 D1 2 1 D2 3 1 D3 4 2 D1 5 2 D4 Expected Results 1 P1 01/01/2011 D1, D2, D3 2 P2 01/02/2011 D1,D4   IDEAS At the begin I got 3 possible ways: - Doing inside the DB:  It could be achieved from DB with a CURSOR in a Stored Procedure. - Doing from .NET with LOOPS. - Doing with LINQ (I love it!!) FIRST APROX Example with a simple CLASS with a LIST: With and Employee Class that acts as Header Table: 1: public class Employee 2: { 3: public Employee () { } 4: public Int32 ID { get; set; } 5: public String FirstName{ get; set; } 6: public String LastName{ get; set; } 7: public List<string> Numbers{ get; set; } // Acts as Details Table 8: } We can show all numbers contained by Employee: 1: List<Employee > listado = new List<Employee >(); 2: //Fill Listado 3: var query= from Employee em in listado 4: let Nums= string.Join(";", em.Numbers) 5: select new { 6: em.Name, 7: Nums 8: }; The “LET” operator allows us to host the results of “Join” of the Numbers List of the Employee Class. A little example. ASAP I will post the second part to achieve the same with Entity Framework. Best Regards

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  • SqlBulkCopy From CSV to SQL Datatable

    - by Swapnil
    I'm using SQL Server 2005, VB.NET 2005. I want to be able to import a very large excel file into a SQL table called "XYZ" I've done this by doing the following: 1. Save the excel file as csv.(Using SaveAs XLCSV option) 2. Build a datatable "ABC" From CSV.(using ODBC Connection and Select * from '*'.csv command) 3. copy the datatable"ABC" into database table "xyz" (using sqlBulkCopy.WriteToServer()) It works fine without any error but when i checked my database i found that data type for some columns has been changed and hence it didn't copy some of the records.Any help would be appreciated

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  • Read only particular fields from CSV File in vb.net

    - by fireBand
    Hi, I have this code to read a CVS file. It reads each line, devides each line by delimiter ',' and stored the field values in array 'strline()' . How do I extract only required fields from the CSV file? For example if I have a CSV File like Type,Group,No,Sequence No,Row No,Date (newline) 0,Admin,3,345678,1,26052010 (newline) 1,Staff,5,78654,3,26052010 I Need only the value of columns Group,Sequence No and date. Thanks in advance for any ideas. Dim myStream As StreamReader = Nothing ' Hold the Parsed Data Dim strlines() As String Dim strline() As String Try myStream = File.OpenText(OpenFile.FileName) If (myStream IsNot Nothing) Then ' Hold the amount of lines already read in a 'counter-variable' Dim placeholder As Integer = 0 strlines = myStream.ReadToEnd().Split(Environment.NewLine) Do While strlines.Length <> -1 ' Is -1 when no data exists on the next line of the CSV file strline = strlines(placeholder).Split(",") placeholder += 1 Loop End If Catch ex As Exception LogErrorException(ex) Finally If (myStream IsNot Nothing) Then myStream.Close() End If End Try

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  • Load data from CSV to mySQL database Java+hibernate+spring

    - by mona
    I am trying to load a CSV file in to mySQL database using Java+Hibernate+Spring. I am using the following query in the DAO to help me load in to the database: entityManager.createQuery("LOAD DATA INFILE :fileName INTO TABLE test").setParameter("fileName", "C:\\samples\\test\\abcd.csv").executeUpdate(); I got some idea to use this from http://dev.mysql.com/doc/refman/5.1/en/load-data.html and how to import a csv file into a mysql from an hibernate+spring application? But I am getting the error: java.lang.IllegalArgumentException: node to traverse cannot be null! Please help! Thanks

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  • Online conversion to CSV using Perl

    - by Octopus
    I have a application generating logs in every 5 sec. The logs are in below format. 11:13:49.250,interface,0,RX,0 11:13:49.250,interface,0,TX,0 11:13:49.250,interface,1,close,0 11:13:49.250,interface,4,error,593 11:13:49.250,interface,4,idle,2994215 and so on for other interfaces... I am working to convert these into below CSV format Time,interface.RX,interface.TX,interface.close.... 11:13:49,0,0,0,.... Simple as of now but the problem is, I have to get the data in csv format online, i.e as soon the log file updated the CSV should also be updated. Is there any way to do this using perl.

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  • Validating Column Data Stored as CSV Against Another Table

    - by Jakkwylde
    I wanted to see what some suggested approaches would be to validate a field that is stored as a CSV against a table containing appropriate values. Althought it would be desired, it is NOT an option to split the CSV list into another related table. In the example data below I would be trying to capture the code 99 for widget A. Below is an example data representation. Table: Widgets WidgetName WidgetCodeList A 1, 2, 3 B 1 C 2, 3 D 99 Table: WidgetCodes WidgetCode 1 2 3 An earlier approach was to query the CSV column as rows using various string manipulations and CONNECT_BY_LEVEL however the performance was not acceptible.

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  • problem reading a csv file in python

    - by Hossein
    Hi, I am trying to read a very simple but somehow large(800Mb) csv file using the csv library in python. The delimiter is a single tab and each line consists of some numbers. Each line is a record, and I have 20681 rows in my file. I had some problems during my calculations using this file,it always stops at a certain row. I got suspicious about the number of rows in the file.I used the code below to count the number of row in this file: tfdf_Reader = csv.reader(open('v2-host_tfdf_en.txt'),delimiter=' ') c = 0 for row in tfdf_Reader: c = c + 1 print c To my surprise c is printed with the value of 61722!!! Why is this happening? What am I doing wrong?

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  • Problem with a large CSV file

    - by moustafa
    I have a very large CSV file. 51427 lines to be exact. I need to import the entire file into a MySQL database, however, the script times out due to server settings and slow connection (and maybe other reasons that I am not aware of). So - I am now passing parameters START and LIMIT via address bar to import, like this: http://my.server.address/import.php?...000&limit=1000 This reads the entire CSV file into an array, and starts at line 10000 of the array and inserts into the database until it reaches line 11000, and then terminates the script. This works very nicely, however, I am not happy having to reach the entire 51427 lines of the CSV file into an array before processing. Is there not a way where I can only read the required lines into an array? That would speed things up significantly.

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  • Event Logging in LINQ C# .NET

    The first thing you'll want to do before using this code is to create a table in your database called TableHistory: CREATE TABLE [dbo].[TableHistory] (     [TableHistoryID] [int] IDENTITY NOT NULL ,     [TableName] [varchar] (50) NOT NULL ,     [Key1] [varchar] (50) NOT NULL ,     [Key2] [varchar] (50) NULL ,     [Key3] [varchar] (50) NULL ,     [Key4] [varchar] (50) NULL ,     [Key5] [varchar] (50) NULL ,     [Key6] [varchar] (50)NULL ,     [ActionType] [varchar] (50) NULL ,     [Property] [varchar] (50) NULL ,     [OldValue] [varchar] (8000) NULL ,     [NewValue] [varchar] (8000) NULL ,     [ActionUserName] [varchar] (50) NOT NULL ,     [ActionDateTime] [datetime] NOT NULL ) Once you have created the table, you'll need to add it to your custom LINQ class (which I will refer to as DboDataContext), thus creating the TableHistory class. Then, you'll need to add the History.cs file to your project. You'll also want to add the following code to your project to get the system date: public partial class DboDataContext{ [Function(Name = "GetDate", IsComposable = true)] public DateTime GetSystemDate() { MethodInfo mi = MethodBase.GetCurrentMethod() as MethodInfo; return (DateTime)this.ExecuteMethodCall(this, mi, new object[] { }).ReturnValue; }}private static Dictionary<type,> _cachedIL = new Dictionary<type,>();public static T CloneObjectWithIL<t>(T myObject){ Delegate myExec = null; if (!_cachedIL.TryGetValue(typeof(T), out myExec)) { // Create ILGenerator DynamicMethod dymMethod = new DynamicMethod("DoClone", typeof(T), new Type[] { typeof(T) }, true); ConstructorInfo cInfo = myObject.GetType().GetConstructor(new Type[] { }); ILGenerator generator = dymMethod.GetILGenerator(); LocalBuilder lbf = generator.DeclareLocal(typeof(T)); //lbf.SetLocalSymInfo("_temp"); generator.Emit(OpCodes.Newobj, cInfo); generator.Emit(OpCodes.Stloc_0); foreach (FieldInfo field in myObject.GetType().GetFields( System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.NonPublic)) { // Load the new object on the eval stack... (currently 1 item on eval stack) generator.Emit(OpCodes.Ldloc_0); // Load initial object (parameter) (currently 2 items on eval stack) generator.Emit(OpCodes.Ldarg_0); // Replace value by field value (still currently 2 items on eval stack) generator.Emit(OpCodes.Ldfld, field); // Store the value of the top on the eval stack into // the object underneath that value on the value stack. // (0 items on eval stack) generator.Emit(OpCodes.Stfld, field); } // Load new constructed obj on eval stack -> 1 item on stack generator.Emit(OpCodes.Ldloc_0); // Return constructed object. --> 0 items on stack generator.Emit(OpCodes.Ret); myExec = dymMethod.CreateDelegate(typeof(Func<t,>)); _cachedIL.Add(typeof(T), myExec); } return ((Func<t,>)myExec)(myObject);}I got both of the above methods off of the net somewhere (maybe even from CodeProject), but it's been long enough that I can't recall where I got them.Explanation of the History ClassThe History class records changes by creating a TableHistory record, inserting the values for the primary key for the table being modified into the Key1, Key2, ..., Key6 columns (if you have more than 6 values that make up a primary key on any table, you'll want to modify this), setting the type of change being made in the ActionType column (INSERT, UPDATE, or DELETE), old value and new value if it happens to be an update action, and the date and Windows identity of the user who made the change.Let's examine what happens when a call is made to the RecordLinqInsert method:public static void RecordLinqInsert(DboDataContext dbo, IIdentity user, object obj){ TableHistory hist = NewHistoryRecord(obj); hist.ActionType = "INSERT"; hist.ActionUserName = user.Name; hist.ActionDateTime = dbo.GetSystemDate(); dbo.TableHistories.InsertOnSubmit(hist);}private static TableHistory NewHistoryRecord(object obj){ TableHistory hist = new TableHistory(); Type type = obj.GetType(); PropertyInfo[] keys; if (historyRecordExceptions.ContainsKey(type)) { keys = historyRecordExceptions[type].ToArray(); } else { keys = type.GetProperties().Where(o => AttrIsPrimaryKey(o)).ToArray(); } if (keys.Length > KeyMax) throw new HistoryException("object has more than " + KeyMax.ToString() + " keys."); for (int i = 1; i <= keys.Length; i++) { typeof(TableHistory) .GetProperty("Key" + i.ToString()) .SetValue(hist, keys[i - 1].GetValue(obj, null).ToString(), null); } hist.TableName = type.Name; return hist;}protected static bool AttrIsPrimaryKey(PropertyInfo pi){ var attrs = from attr in pi.GetCustomAttributes(typeof(ColumnAttribute), true) where ((ColumnAttribute)attr).IsPrimaryKey select attr; if (attrs != null && attrs.Count() > 0) return true; else return false;}RecordLinqInsert takes as input a data context which it will use to write to the database, the user, and the LINQ object to be recorded (a single object, for instance, a Customer or Order object if you're using AdventureWorks). It then calls the NewHistoryRecord method, which uses LINQ to Objects in conjunction with the AttrIsPrimaryKey method to pull all the primary key properties, set the Key1-KeyN properties of the TableHistory object, and return the new TableHistory object. The code would be called in an application, like so: Continue span.fullpost {display:none;}

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  • Performance issue when configuring non HA VM in cluster

    - by laiys
    Hi, I saw this article http://technet.microsoft.com/en-us/library/cc764243.aspx Quote taken from the link “ Important It is recommended that you not deploy virtual machines that are not highly available on your host clusters. Although you can do this by using Hyper-V (VMM does not allow it), the non-highly available virtual machines will consume resources that otherwise would be available to the HAVMs What kind of resources (CPU,memory, NIC, etc) that non HA VM will consume? Just curious as not all VM (in production) not to be in Failover Cluster and Live Migration. If i put the VM into CSV but did not make it as HA, what impact does it make since i allocate same vCPU, vNic and VMemory into the VM. (not to mention that i lost failover feature). Curious to understand more about this. Please advise. Thanks

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