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  • How can i query for null values in entity framework?

    - by AZ
    I want to execute a query like this var result = from entry in table where entry.something == null select entry; and get an IS NULL generated. Edited: After the first two answers i feel the need to clarify that I'm using Entity Framework and not Linq to SQL. The object.Equals() method does not seem to work in EF. Edit no.2: The above query works as intended. It correctly generates IS NULL. My production code however was var value = null; var result = from entry in table where entry.something == value select entry; and the generated SQL was something = @p; @p = NULL. It seems that EF correctly translates the constant expression but if a variable is involved it treats it just like a normal comparison. Makes sense actually. I'll close this question

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  • Is it possible to easily convert SqlCommand to T-SQL string ?

    - by Thomas Wanner
    I have a populated SqlCommand object containing the command text and parameters of various database types along with their values. What I need is a T-SQL script that I could simply execute that would have the same effect as calling the ExecuteNonQuery method on the command object. Is there an easy way to do such "script dump" or do I have to manually construct such script from the command object ?

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  • Can Entity Framework be used for the purpose of entity/schema definition at application runtime?

    - by Kabeer
    Hello. Can 'Entity Framework' be used for the purpose of entity definition at application runtime? Ok, to make it simple, here is what I want to achieve: My application is a product. I should be able to define entities at runtime on the basis of inputs gathered from an 'authoring' user (in effect this means 'model first' approach). These entities are of course persistable. Further, after having defined the entities and their relationships, I should be able to make complex queries across them for many reasons, including reports. Is the above possible and how? So far what I have realized is that there is a dependency on Visual Studio.

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  • WCF Data Services - neither .Expand or .LoadProperty seems to do what I need

    - by TomK
    I am building a school management app where they track student tardiness and absences. I've got three entities to help me in this. A Students entity (first name, last name, ID, etc.); a SystemAbsenceTypes entity with SystemAbsenceTypeID values for Late, Absent-with-Reason, Absent-without-Reason; and a cross-reference table called StudentAbsences (matching the student IDs with the absence-type ID, plus a date, and a Notes field). What I want to do is query my entities for a given student, and then add up the number of each kind of Absence, for a given date range. I prepare my currentStudent object without a problem, then I do this... Me.Data.LoadProperty(currentStudent, "StudentAbsences") 'Loads the cross-ref data lblDaysLate.Text = (From ab In currentStudent.StudentAbsences Where ab.SystemAbsenceTypes.SystemAbsenceTypeID = Common.enuStudentAbsenceTypes.Late).Count.ToString ...and this second line fails, complaining it has no value for an object. I presume the problem is that while it DOES see that there are (let's say) four absences for the currentStudent (ie, currentStudent.StudentAbsences.Count = 4) -- it can't yet "peer into" each one of the absences to look at its type. How do I use .Expand or .LoadProperty to make this happen? I tried fiddling with .LoadProperty but it doesn't take a two-level syntax like so... Data.LoadProperty(currentStudent,"StudentAbsences.SystemAbsenceTypeID") or the like. Is there some other technique?

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  • crash with CoUnintialize() api of COM

    - by jbp117
    My main process(main.exe) initilaized COM library and created a thread which creates a new process(p1.exe) this new process is again initializing COM library and after making all references as zero unintialized COM here.. the unintailezed COM in the main process (i.e main.exe) also.... When i run p1.exe individually it is successful.. but it is crashing when i create a process for p1.exe from main.exe

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  • Updating a Data Source with a Dataset

    - by Paul
    Hi, I need advice. I have asp.net web service and winforms client app. Client call this web method and get dataset. 1. [WebMethod] 2. public DataSet GetSecureDataSet(string id) 3. { 4. 5. 6. SqlConnection conn = null; 7. SqlDataAdapter da = null; 8. DataSet ds; 9. try 10. { 11. 12. string sql = "SELECT * FROM Tab1"; 13. 14. string connStr = WebConfigurationManager.ConnectionStrings["Employees"].ConnectionString; 15. 16. conn = new SqlConnection(connStr); 17. conn.Open(); 18. 19. da = new SqlDataAdapter(sql, conn); 20. 21. ds = new DataSet(); 22. da.Fill(ds, "Tab1"); 23. 24. return ds; 25. } 26. catch (Exception ex) 27. { 28. throw ex; 29. } 30. finally 31. { 32. if (conn != null) 33. conn.Close(); 34. if (da != null) 35. da.Dispose(); 36. } 37. } After he finish work he call this update web method. He can add, delete and edit rows in table in dataset. [WebMethod] public bool SecureUpdateDataSet(DataSet ds) { SqlConnection conn = null; SqlDataAdapter da = null; SqlCommand cmd = null; try { DataTable delRows = ds.Tables[0].GetChanges(DataRowState.Deleted); DataTable addRows = ds.Tables[0].GetChanges(DataRowState.Added); DataTable editRows = ds.Tables[0].GetChanges(DataRowState.Modified); string sql = "UPDATE * FROM Tab1"; string connStr = WebConfigurationManager.ConnectionStrings["Employees"].ConnectionString; conn = new SqlConnection(connStr); conn.Open(); cmd = new SqlCommand(sql, conn); da = new SqlDataAdapter(sql, conn); if (addRows != null) { da.Update(addRows); } if (delRows != null) { da.Update(delRows); } if (editRows != null) { da.Update(editRows); } return true; } catch (Exception ex) { throw ex; } finally { if (conn != null) conn.Close(); if (da != null) da.Dispose(); } } Code on client side 1. //on client side is dataset bind to datagridview 2. Dataset ds = proxy.GetSecureDataSet(""); 3. ds.AcceptChanges(); 4. 5. //edit dataset 6. 7. 8. //get changes 9. DataSet editDataset = ds.GetChanges(); 10. 11. //call update webmethod 12. proxy.SecureUpdateDataSet(editDataSet) But it finish with this error : System.Web.Services.Protocols.SoapException: Server was unable to process request. --- System.InvalidOperationException: Update requires a valid UpdateCommand when passed DataRow collection with modified rows. at WebService.Service.SecureUpdateDataSet(DataSet ds) in D:\Diploma.Work\WebService\Service1.asmx.cs:line 489 Problem is with SQL Commad, client can add, delete and insert row, how can write a corect SQL command.... any advice please? Thank you

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  • Importing an Excel WorkSheet into a Datatable

    - by Nick LaMarca
    I have been asked to create import functionality in my application. I am getting an excel worksheet as input. The worksheet has column headers followed by data. The users want to simply select an xls file from their system, click upload and the tool deletes the table in the database and adds this new data. I thought the best way would be too bring the data into a datatable object and do a foeach for every row in the datatable insert row by row into the db. My question is what can anyone give me code to open an excel file, know what line the data starts on in the file, and import the data into a datable object?

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  • Possible to view T-SQL syntax of a stored proc-based SqlCommand?

    - by mconnley
    Hello! I was wondering if anybody knows of a way to retrieve the actual T-SQL that is to be executed by a SqlCommand object (with a CommandType of StoredProcedure) before it executes... My scenario involves optionally saving DB operations to a file or MSMQ before the command is actually executed. My assumption is that if you create a SqlCommand like the following: Using oCommand As New SqlCommand("sp_Foo") oCommand.CommandType = CommandType.StoredProcedure oCommand.Parameters.Add(New SqlParameter("@Param1", "value1")) oCommand.ExecuteNonQuery() End Using It winds up executing some T-SQL like: EXEC sp_Foo @Param1 = 'value1' Is that assumption correct? If so, is it possible to retrieve that actual T-SQL somehow? My goal here is to get the parsing, etc. benefits of using the SqlCommand class since I'm going to be using it anyway. Is this possible? Am I going about this the wrong way? Thanks in advance for any input!

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  • Specification of Extended Properties in OleDb connection string?

    - by Monty
    At the moment I'm searching for properties for a connection string, which can be used to connect to an Excel file in readonly mode. Searching Google gets me a lot of examples of connection strings, but I can't seem to find a specification of all possibilities in the 'Extended Properties' section of the OleDb connection string. At the moment I've this: Provider = Microsoft.Jet.OLEDB.4.0; Data Source = D:\Data\Customers.xls; Extended Properties = 'Excel 8.0; Mode=Read; ReadOnly=true; HDR=Yes'; However... I've composed this by examples. So questions: 1. What is a decent source for OleDb Connection String documentation/reference? 2. Is the above connection string indeed connecting to the Excel file in readonly mode? Thanks!

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  • Can I get a reference to a pending transaction from a SqlConnection object?

    - by Rune
    Hey, Suppose someone (other than me) writes the following code and compiles it into an assembly: using (SqlConnection conn = new SqlConnection(connString)) { conn.Open(); using (var transaction = conn.BeginTransaction()) { /* Update something in the database */ /* Then call any registered OnUpdate handlers */ InvokeOnUpdate(conn); transaction.Commit(); } } The call to InvokeOnUpdate(IDbConnection conn) calls out to an event handler that I can implement and register. Thus, in this handler I will have a reference to the IDbConnection object, but I won't have a reference to the pending transaction. Is there any way in which I can get a hold of the transaction? In my OnUpdate handler I want to execute something similar to the following: private void MyOnUpdateHandler(IDbConnection conn) { var cmd = conn.CreateCommand(); cmd.CommandText = someSQLString; cmd.CommandType = CommandType.Text; cmd.ExecuteNonQuery(); } However, the call to cmd.ExecuteNonQuery() throws an InvalidOperationException complaining that "ExecuteNonQuery requires the command to have a transaction when the connection assigned to the command is in a pending local transaction. The Transaction property of the command has not been initialized". Can I in any way enlist my SqlCommand cmd with the pending transaction? Can I retrieve a reference to the pending transaction from the IDbConnection object (I'd be happy to use reflection if necessary)?

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  • How to I serialize a large graph of .NET object into a SQL Server BLOB without creating a large bu

    - by Ian Ringrose
    We have code like: ms = New IO.MemoryStream bin = New System.Runtime.Serialization.Formatters.Binary.BinaryFormatter bin.Serialize(ms, largeGraphOfObjects) dataToSaveToDatabase = ms.ToArray() // put dataToSaveToDatabase in a Sql server BLOB But the memory steam allocates a large buffer from the large memory heap that is giving us problems. So how can we stream the data without needing enough free memory to hold the serialized objects. I am looking for a way to get a Stream from SQL server that can then be passed to bin.Serialize() so avoiding keeping all the data in my processes memory. Likewise for reading the data back... Some more background. This is part of a complex numerical processing system that processes data in near real time looking for equipment problems etc, the serialization is done to allow a restart when there is a problem with data quality from a data feed etc. (We store the data feeds and can rerun them after the operator has edited out bad values.) Therefore we serialize the object a lot more often then we de-serialize them. The objects we are serializing include very large arrays mostly of doubles as well as a lot of small “more normal” objects. We are pushing the memory limit on a 32 bit system and make the garage collector work very hard. (Effects are being made elsewhere in the system to improve this, e.g. reusing large arrays rather then create new arrays.) Often the serialization of the state is the last straw that courses an out of memory exception; our peak memory usage is while this serialization is being done. I think we get large memory pool fragmentation when we de-serialize the object, I expect there are also other problem with large memory pool fragmentation given the size of the arrays. (This has not yet been investigated, as the person that first looked at this is a numerical processing expert, not a memory management expert.) Are customers use a mix of Sql Server 2000, 2005 and 2008 and we would rather not have different code paths for each version of Sql Server if possible. We can have many active models at a time (in different process, across many machines), each model can have many saved states. Hence the saved state is stored in a database blob rather then a file. As the spread of saving the state is important, I would rather not serialize the object to a file, and then put the file in a BLOB one block at a time. Other related questions I have asked How to Stream data from/to SQL Server BLOB fields? Is there a SqlFileStream like class that works with Sql Server 2005?

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  • How to connect an existing strongly-typed data set to a different server at run time?

    - by Kiril
    I am coding a simple space empire management game in Visual C# 2008, which relies on connecting to a remote SQL server database to get/store data. I would like the user to be able to connect to a user-specified SQL server from the login screen(he specifies IP address, port, database name, ID, password and presses "connect" button). However, I found out that the Dataset connection string property is read only and cannot be changed. Is there any way to guide the wizard-generated DataSet to a user-specified server at run time?

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  • DataReader-DataSet Hybrid solution

    - by G33kKahuna
    My solution architects and I have exhausted both pure Dataset and Datareader solutions. Basically we have a Microsoft.NET 2.0 windows service application that pulls data based on a query and processes additional tasks per record; almost a poor mans workflow system. The recordsets are broader (in terms of the columns) and deeper (in terms of number of records). We observed that DataSet performs much better in terms of performance but runs into contraints as # of records increase say 100K+ we start seeing System.OutOfMemoryException on a 4G machine with processModel configured to run at memoryLimit set to 85. Since this is a multi-threaded app, there could be multiple threads processing different queries and building different DataSets, so we run into the exception sooner in that case DataReader on the other hand works but is a lot slower and hits other contraints; if there is some sort of disconnect it has to start over again or leaves open connections on the DB side and worst case takes down the service completely etc. So, we decided the best option would be some sort of hybrid solution. I'm open to guidance and suggestions. Are there any hybrid solutions available? Any other suggestions

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  • Using LinqExtender to make OData feed fails

    - by BurningIce
    A pretty simple question, has anyone here tried to make a OData feed based on a IQueryable created with LinqExtender? I have created a simple Linq-provider that supports Where, Select, OrderBy and Take and wanted to expose it as an OData Feed. I keep getting an error though, and the Exception is a NullReference with the following StackTrace at System.Data.Services.Serializers.Serializer.GetObjectKey(Object resource, IDataServiceProvider provider, String containerName) at System.Data.Services.Serializers.Serializer.GetUri(Object resource, IDataServiceProvider provider, ResourceContainer container, Uri absoluteServiceUri) at System.Data.Services.Serializers.SyndicationSerializer.WriteEntryElement(IExpandedResult expanded, Object element, Type expectedType, Uri absoluteUri, String relativeUri, SyndicationItem target) at System.Data.Services.Serializers.SyndicationSerializer.<DeferredFeedItems>d__0.MoveNext() at System.ServiceModel.Syndication.Atom10FeedFormatter.WriteItems(XmlWriter writer, IEnumerable`1 items, Uri feedBaseUri) at System.ServiceModel.Syndication.Atom10FeedFormatter.WriteFeedTo(XmlWriter writer, SyndicationFeed feed, Boolean isSourceFeed) at System.ServiceModel.Syndication.Atom10FeedFormatter.WriteFeed(XmlWriter writer) at System.ServiceModel.Syndication.Atom10FeedFormatter.WriteTo(XmlWriter writer) at System.Data.Services.Serializers.SyndicationSerializer.WriteTopLevelElements(IExpandedResult expanded, IEnumerator elements, Boolean hasMoved) at System.Data.Services.Serializers.Serializer.WriteRequest(IEnumerator queryResults, Boolean hasMoved) at System.Data.Services.ResponseBodyWriter.Write(Stream stream) I've kinda narrowed it down to a issue where LinqExtender wraps every returned object, so that my object actually inherits itself - thats at least how it looks like in the debugger. These two queries are basicly the same. The first is the legacy-api where the OrderBy and Select is regular Linq to Objects. The second query is a "real" linq-provider made with LinqExtender. var db = CalendarDataProvider.GetCalendarEntriesByDate(DateTime.Now, DateTime.Now.AddMonths(1), Guid.Empty) .OrderBy(o => o.Title) .Select(o => new ODataCalendarEntry(o)); var query = new ODataCalendarEntryQuery() .Where(o => o.Start > DateTime.Now && o.End < DateTime.Now.AddMonths(1)) .OrderBy(o => o.Title); When returning db for the OData feed everything is fine, but returning query throws a NullRefenceException. I've tried all kind of tricks and even tried to project all the data into a new object like this, but still the same error return query.Select(o => new ODataCalendarEntry { Title = o.Title, Start = o.Start, End = o.End, Name = o.Name });

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  • Conversion failed: SqlParameter and DateTime

    - by Tim
    I'm changing old,vulnerable sqlcommands with SqlParameters but get a SqlException: System.Data.SqlClient.SqlException {"Conversion failed when converting datetime from character string."} on sqlCommand.ExecuteScalar() Dim sqlString As String = _ "SELECT TOP 1 " & _ "fiSL " & _ "FROM " & _ "tabData AS D " & _ "WHERE " & _ "D.SSN_Number = '@SSN_Number' " & _ "AND D.fiProductType = 1 " & _ "AND D.Repair_Completion_Date > '@Repair_Completion_Date' " & _ "ORDER BY " & _ "D.Repair_Completion_Date ASC" Dim obj As Object Dim sqlCommand As SqlCommand Try sqlCommand = New SqlCommand(sqlString, Common.MyDB.SqlConn_RM2) sqlCommand.CommandTimeout = 120 sqlCommand.Parameters.AddWithValue("@SSN_Number", myClaim.SSNNumber) sqlCommand.Parameters.AddWithValue("@Repair_Completion_Date", myClaim.RepairCompletionDate) If Common.MyDB.SqlConn_RM2.State <> System.Data.ConnectionState.Open Then Common.MyDB.SqlConn_RM2.Open() obj = sqlCommand.ExecuteScalar() Catch ex As Exception Dim debug As String = ex.ToString Finally Common.MyDB.SqlConn_RM2.Close() End Try myClaim.RepairCompletionDate is a SQLDateTime. Do i have to remove the quotes in the sqlString to compare Date columns? But then i dont get a exception but incorrect results.

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  • Auditing in Entity Framework.

    - by Gabriel Susai
    After going through Entity Framework I have a couple of questions on implementing auditing in Entity Framework. I want to store each column values that is created or updated to a different audit table. Rightnow I am calling SaveChanges(false) to save the records in the DB(still the changes in context is not reset). Then get the added | modified records and loop through the GetObjectStateEntries. But don't know how to get the values of the columns where their values are filled by stored proc. ie, createdate, modifieddate etc. Below is the sample code I am working on it. //Get the changed entires( ie, records) IEnumerable<ObjectStateEntry> changes = context.ObjectStateManager.GetObjectStateEntries(EntityState.Modified); //Iterate each ObjectStateEntry( for each record in the update/modified collection) foreach (ObjectStateEntry entry in changes) { //Iterate the columns in each record and get thier old and new value respectively foreach (var columnName in entry.GetModifiedProperties()) { string oldValue = entry.OriginalValues[columnName].ToString(); string newValue = entry.CurrentValues[columnName].ToString(); //Do Some Auditing by sending entityname, columnname, oldvalue, newvalue } } changes = context.ObjectStateManager.GetObjectStateEntries(EntityState.Added); foreach (ObjectStateEntry entry in changes) { if (entry.IsRelationship) continue; var columnNames = (from p in entry.EntitySet.ElementType.Members select p.Name).ToList(); foreach (var columnName in columnNames) { string newValue = entry.CurrentValues[columnName].ToString(); //Do Some Auditing by sending entityname, columnname, value } }

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  • why DbCommandBuilder (Oracle) produces weird WHERE-clause to UpdateCommand?

    - by matti
    I have a table HolidayHome in oracle db which has unique db index on Id (I haven't specified this in the code in any way for adapter/table/dataset, don't know if i should/can). DbDataAdapter.SelectCommand is like this: SELECT Id, ExtId, Label, Location1, Location2, Location3, Location4, ClassId, X, Y, UseType FROM HolidayHome but UpdateCommand generated by DbCommandBuilder has very weird where clause: UPDATE HOLIDAYHOME SET ID = :p1, EXTID = :p2, LABEL = :p3, LOCATION1 = :p4, LOCATION2 = :p5, LOCATION3 = :p6, LOCATION4 = :p7, CLASSID = :p8, X = :p9, Y = :p10, USETYPE = :p11 WHERE ((ID = :p12) AND ((:p13 = 1 AND EXTID IS NULL) OR (EXTID = :p14)) AND ((:p15 = 1 AND LABEL IS NULL) OR (LABEL = :p16)) AND ((:p17 = 1 AND LOCATION1 IS NULL) OR (LOCATION1 = :p18)) AND ((:p19 = 1 AND LOCATION2 IS NULL) OR (LOCATION2 = :p20)) AND ((:p21 = 1 AND LOCATION3 IS NULL) OR (LOCATION3 = :p22)) AND ((:p23 = 1 AND LOCATION4 IS NULL) OR (LOCATION4 = :p24)) AND (CLASSID = :p25) AND (X = :p26) AND (Y = :p27) AND (USETYPE = :p28)) all these fields that have like: ((:p17 = 1 AND LOCATION1 IS NULL) OR (LOCATION1 = :p18)) are defined in oracle db like this: LOCATION1 VARCHAR2(30) so they allow null values. the code looks like this: static bool CreateInsertUpdateDeleteCmds(DbDataAdapter dataAdapter) { DbCommandBuilder builder = _trgtProvFactory.CreateCommandBuilder(); builder.DataAdapter = dataAdapter; // Get the insert, update and delete commands. dataAdapter.InsertCommand = builder.GetInsertCommand(); dataAdapter.UpdateCommand = builder.GetUpdateCommand(); dataAdapter.DeleteCommand = builder.GetDeleteCommand(); } what to do? The UpdateCommand is utter madness. Thanks & Best Regards: Matti

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  • Cyclic References and WCF

    - by Kunal
    I have generated my POCO entities using POCO Generator, I have more than 150+ tables in my database. I am sharing POCO entities all across the application layers including the client. I have disabled both LazyLoading and ProxyCreation in my context.I am using WCF on top of my data access and business layer. Now, When I return a poco entity to my client, I get an error saying "Underlying connection was closed" I enabled WCF tracing and found the exact error : Contains cycles and cannot be serialized if reference tracking is disabled. I Looked at MSDN and found solutions like setting IsReference=true in the DataContract method atttribute but I am not decorating my POCO classes with DataContracts and I assume there is no need of it as well. I won't be calling that as a POCO if I decorate a class with DataContract attribute Then, I found solutions like applying custom attribute [CyclicReferenceAware] over my ServiceContracts.That did work but I wanted to throw this question to community to see how other people managed this and also why Microsoft didn't give built in support for figuring out cyclic references while serializing POCO classes

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  • How can i return IEnumarable data from function in GridView with Entity FrameWork?

    - by programmerist
    protected IEnumerable GetPersonalsData() { // List personel; using (FirmaEntities firmactx = new FirmaEntities()) { var personeldata = (from p in firmactx.Personals select new { p.ID, p.Name, p.SurName }); return personeldata.AsEnumerable(); } } i wan to send GetPersonelData() into GridView DataSource. Like That: gwPersonel.DataSource = GetPersonelData(); gwPersonel.DataBind(); it monitored to me on : gwPersonel.DataBind(); this error: "The ObjectContext instance has been disposed and can no longer be used for operations that require a connection."

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  • how to get group total in self refrenced data in data table ?

    - by Nikhil Vaghela
    I have three columns in my data table. 1) ProductID 2) ProductParentID 3) ProductTotal ProductID and ProductParentID are self refrencing columns where i can set parent child relationship and get child rows based on my relationship. Let us say i have following data Product1     Product11     Product12     Product13         Product131         Product132         Product133 Product2     Product21     Product22     Product23 Next to above hierarchy in Product total column what i want is total of each child rows and sum of those child rows product total should be rolled up to it parent product. E.g if Product 131 total is 10,Product 13 total is 15 and Product 133 total is 5 then the product 13 total should be 30. The logic should work for n number of self hierarchy. Is there any functionality in data table itself where i can achieve this without iterating through each row and do it manually ? Thanks.

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