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• SQL SERVER – Parsing SSIS Catalog Messages – Notes from the Field #030

  - by Pinal Dave

  [Note from Pinal]: This is a new episode of Notes from the Field series. SQL Server Integration Service (SSIS) is one of the most key essential part of the entire Business Intelligence (BI) story. It is a platform for data integration and workflow applications. The tool may also be used to automate maintenance of SQL Server databases and updates to multidimensional cube data. In this episode of the Notes from the Field series I requested SSIS Expert Andy Leonard to discuss one of the most interesting concepts of SSIS Catalog Messages. There are plenty of interesting and useful information captured in the SSIS catalog and we will learn together how to explore the same. The SSIS Catalog captures a lot of cool information by default. Here’s a query I use to parse messages from the catalog.operation_messages table in the SSISDB database, where the logged messages are stored. This query is set up to parse a default message transmitted by the Lookup Transformation. It’s one of my favorite messages in the SSIS log because it gives me excellent information when I’m tuning SSIS data flows. The message reads similar to: Data Flow Task:Information: The Lookup processed 4485 rows in the cache. The processing time was 0.015 seconds. The cache used 1376895 bytes of memory. The query: USE SSISDB GO DECLARE @MessageSourceType INT = 60 DECLARE @StartOfIDString VARCHAR(100) = 'The Lookup processed ' DECLARE @ProcessingTimeString VARCHAR(100) = 'The processing time was ' DECLARE @CacheUsedString VARCHAR(100) = 'The cache used ' DECLARE @StartOfIDSearchString VARCHAR(100) = '%' + @StartOfIDString + '%' DECLARE @ProcessingTimeSearchString VARCHAR(100) = '%' + @ProcessingTimeString + '%' DECLARE @CacheUsedSearchString VARCHAR(100) = '%' + @CacheUsedString + '%' SELECT operation_id , SUBSTRING(MESSAGE, (PATINDEX(@StartOfIDSearchString,MESSAGE) + LEN(@StartOfIDString) + 1), ((CHARINDEX(' ', MESSAGE, PATINDEX(@StartOfIDSearchString,MESSAGE) + LEN(@StartOfIDString) + 1)) - (PATINDEX(@StartOfIDSearchString, MESSAGE) + LEN(@StartOfIDString) + 1))) AS LookupRowsCount , SUBSTRING(MESSAGE, (PATINDEX(@ProcessingTimeSearchString,MESSAGE) + LEN(@ProcessingTimeString) + 1), ((CHARINDEX(' ', MESSAGE, PATINDEX(@ProcessingTimeSearchString,MESSAGE) + LEN(@ProcessingTimeString) + 1)) - (PATINDEX(@ProcessingTimeSearchString, MESSAGE) + LEN(@ProcessingTimeString) + 1))) AS LookupProcessingTime , CASE WHEN (CONVERT(numeric(3,3),SUBSTRING(MESSAGE, (PATINDEX(@ProcessingTimeSearchString,MESSAGE) + LEN(@ProcessingTimeString) + 1), ((CHARINDEX(' ', MESSAGE, PATINDEX(@ProcessingTimeSearchString,MESSAGE) + LEN(@ProcessingTimeString) + 1)) - (PATINDEX(@ProcessingTimeSearchString, MESSAGE) + LEN(@ProcessingTimeString) + 1))))) = 0 THEN 0 ELSE CONVERT(bigint,SUBSTRING(MESSAGE, (PATINDEX(@StartOfIDSearchString,MESSAGE) + LEN(@StartOfIDString) + 1), ((CHARINDEX(' ', MESSAGE, PATINDEX(@StartOfIDSearchString,MESSAGE) + LEN(@StartOfIDString) + 1)) - (PATINDEX(@StartOfIDSearchString, MESSAGE) + LEN(@StartOfIDString) + 1)))) / CONVERT(numeric(3,3),SUBSTRING(MESSAGE, (PATINDEX(@ProcessingTimeSearchString,MESSAGE) + LEN(@ProcessingTimeString) + 1), ((CHARINDEX(' ', MESSAGE, PATINDEX(@ProcessingTimeSearchString,MESSAGE) + LEN(@ProcessingTimeString) + 1)) - (PATINDEX(@ProcessingTimeSearchString, MESSAGE) + LEN(@ProcessingTimeString) + 1)))) END AS LookupRowsPerSecond , SUBSTRING(MESSAGE, (PATINDEX(@CacheUsedSearchString,MESSAGE) + LEN(@CacheUsedString) + 1), ((CHARINDEX(' ', MESSAGE, PATINDEX(@CacheUsedSearchString,MESSAGE) + LEN(@CacheUsedString) + 1)) - (PATINDEX(@CacheUsedSearchString, MESSAGE) + LEN(@CacheUsedString) + 1))) AS LookupBytesUsed ,CASE WHEN (CONVERT(bigint,SUBSTRING(MESSAGE, (PATINDEX(@StartOfIDSearchString,MESSAGE) + LEN(@StartOfIDString) + 1), ((CHARINDEX(' ', MESSAGE, PATINDEX(@StartOfIDSearchString,MESSAGE) + LEN(@StartOfIDString) + 1)) - (PATINDEX(@StartOfIDSearchString, MESSAGE) + LEN(@StartOfIDString) + 1)))))= 0 THEN 0 ELSE CONVERT(bigint,SUBSTRING(MESSAGE, (PATINDEX(@CacheUsedSearchString,MESSAGE) + LEN(@CacheUsedString) + 1), ((CHARINDEX(' ', MESSAGE, PATINDEX(@CacheUsedSearchString,MESSAGE) + LEN(@CacheUsedString) + 1)) - (PATINDEX(@CacheUsedSearchString, MESSAGE) + LEN(@CacheUsedString) + 1)))) / CONVERT(bigint,SUBSTRING(MESSAGE, (PATINDEX(@StartOfIDSearchString,MESSAGE) + LEN(@StartOfIDString) + 1), ((CHARINDEX(' ', MESSAGE, PATINDEX(@StartOfIDSearchString,MESSAGE) + LEN(@StartOfIDString) + 1)) - (PATINDEX(@StartOfIDSearchString, MESSAGE) + LEN(@StartOfIDString) + 1)))) END AS LookupBytesPerRow FROM [catalog].[operation_messages] WHERE message_source_type = @MessageSourceType AND MESSAGE LIKE @StartOfIDSearchString GO Note that you have to set some parameter values: @MessageSourceType [int] – represents the message source type value from the following results: Value     Description 10           Entry APIs, such as T-SQL and CLR Stored procedures 20           External process used to run package (ISServerExec.exe) 30           Package-level objects 40           Control Flow tasks 50           Control Flow containers 60           Data Flow task 70           Custom execution message Note: Taken from Reza Rad’s (excellent!) helper.MessageSourceType table found here. @StartOfIDString [VarChar(100)] – use this to uniquely identify the message field value you wish to parse. In this case, the string ‘The Lookup processed ‘ identifies all the Lookup Transformation messages I desire to parse. @ProcessingTimeString [VarChar(100)] – this parameter is message-specific. I use this parameter to specifically search the message field value for the beginning of the Lookup Processing Time value. For this execution, I use the string ‘The processing time was ‘. @CacheUsedString [VarChar(100)] – this parameter is also message-specific. I use this parameter to specifically search the message field value for the beginning of the Lookup Cache  Used value. It returns the memory used, in bytes. For this execution, I use the string ‘The cache used ‘. The other parameters are built from variations of the parameters listed above. The query parses the values into text. The string values are converted to numeric values for ratio calculations; LookupRowsPerSecond and LookupBytesPerRow. Since ratios involve division, CASE statements check for denominators that equal 0. Here are the results in an SSMS grid: This is not the only way to retrieve this information. And much of the code lends itself to conversion to functions. If there is interest, I will share the functions in an upcoming post. If you want to get started with SSIS with the help of experts, read more over at Fix Your SQL Server. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: Notes from the Field, PostADay, SQL, SQL Authority, SQL Backup and Restore, SQL Query, SQL Server, SQL Tips and Tricks, T SQL Tagged: SSIS

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• Why LINQ to Entities won't let me initialize just some properties of an Entity?

  - by emzero

  So I've started to add Entity Framework 4 into a legacy web application (ASP.NET WebForms). As a start I have auto-generated some entities from the database. Also I want to apply Repository Pattern. There is an entity called Visitor and its repository VisitorRepository In VisitorRepository I have the following method: public IEnumerable<Visitor> GetActiveVisitors() { var visitors = from v in _context.Visitors where v.IsActive select new Visitor { VisitorID = v.VisitorID, EmailAddress = v.EmailAddress, RegisterDate = v.RegisterDate, Company = v.Company, Position = v.Position, FirstName = v.FirstName, LastName = v.LastName }; return visitors.ToList(); } That List is then bound to a repeater and when trying to do <%# Eval('EmailAddress') #%> it throws the following exception. The entity or complex type 'Model.Visitor' cannot be constructed in a LINQ to Entities query. A) Why is this happening? How I can workaround this? Do I need to select an anonymous type and then use that to initialize my entities??? B) Why every example I've seen makes use of 'select new' (anonymous object) instead of initializing a known type? Anonymous types are useless unless you are retrieving the data and showing it in the same layer. As far as I know anonymous types cannot be returned from methods? So what's the real point of them??? Thank you all

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• Linq The specified type 'string' is not a valid provider type.

  - by Joe Pitz

  Using Linq to call a stored procedure that passes a single string, The stored procedure returns a data set row that contains a string and an int. Code: PESQLDataContext pe = new PESQLDataContext(strConnStr); pe.ObjectTrackingEnabled = false; gvUnitsPassed.DataSource = pe.PassedInspection(Line); gvUnitsPassed.DataBind(); pe.dispose(); When the code runs an exception gets called below: The exception is thrown at the IExecuteResult result = statement: Enclosed is my result class in the designer.cs file. [Function(Name = "dbo.PassedInspection")] public ISingleResult<PassedInspectionResult> PassedInspection([Parameter(Name = "Model", DbType = "VarChar(4)")] string model) { IExecuteResult result = this.ExecuteMethodCall(this, ((MethodInfo)(MethodInfo.GetCurrentMethod())), model); return ((ISingleResult<PassedInspectionResult>)(result.ReturnValue)); } public partial class PassedInspectionResult { private string _Date; private int _Passed; public PassedInspectionResult() { } [Column(Storage = "_Date", DbType = "string NULL")] public string Date { get { return this._Date; } set { if ((this._Date != value)) { this._Date = value; } } } [Column(Storage = "_Passed", DbType = "Int NULL")] public int Passed { get { return this._Passed; } set { if ((this._Passed != value)) { this._Passed = value; } } } } } I have other stored procedures with similar arguments that run just fine. Thanks

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• Validate MVC 2 form using Data annotations and Linq-to-SQL, before the model binder kicks in (with D

  - by Stefanvds

  I'm using linq to SQL and MVC2 with data annotations and I'm having some problems on validation of some types. For example: [DisplayName("Geplande sessies")] [PositiefGeheelGetal(ErrorMessage = "Ongeldige ingave. Positief geheel getal verwacht")] public string Proj_GeplandeSessies { get; set; } This is an integer, and I'm validating to get a positive number from the form. public class PositiefGeheelGetalAttribute : RegularExpressionAttribute { public PositiefGeheelGetalAttribute() : base(@"\d{1,7}") { } } Now the problem is that when I write text in the input, I don't get to see THIS error, but I get the errormessage from the modelbinder saying "The value 'Tomorrow' is not valid for Geplande sessies." The code in the controller: [HttpPost] public ActionResult Create(Projecten p) { if (ModelState.IsValid) { _db.Projectens.InsertOnSubmit(p); _db.SubmitChanges(); return RedirectToAction("Index"); } else { SelectList s = new SelectList(_db.Verbonds, "Verb_ID", "Verb_Naam"); ViewData["Verbonden"] = s; } return View(); } What I want is being able to run the Data Annotations before the Model binder, but that sounds pretty much impossible. What I really want is that my self-written error messages show up on the screen. I have the same problem with a DateTime, which i want the users to write in the specific form 'dd/MM/yyyy' and i have a regex for that. but again, by the time the data-annotations do their job, all i get is a DateTime Object, and not the original string. So if the input is not a date, the regex does not even run, cos the data annotations just get a null, cos the model binder couldn't make it to a DateTime. Does anyone have an idea how to make this work?

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• How can I access the group of a linq group-by query from a nested repeater control?

  - by Duke

  I'm using a linq group by query (with two grouping parameters) and would like to use the resulting data in a nested repeater. var dateGroups = from row in data.AsEnumerable() group row by new { StartDate = row["StartDate"], EndDate = row["EndDate"] }; "data" is a DataTable from an SqlDataAdapter-filled DataSet. "dateGroups" is used in the parent repeater, and I can access the group keys using Eval("key.StartDate") and Eval("key.EndDate"). Since dateGroups actually contains all the data rows grouped neatly by Start/End date, I'd like to access those rows to display the data in a child repeater. To what would I set the child repeater's DataSource? I have tried every expression in markup I could think of; I think the problem is that I'm trying to access an anonymous member (and I don't know how.) In case it doesn't turn out to be obvious, what would be the expression to access the elements in each iteration of the child repeater? Is there an expression that would let me set the DataSource in the markup, or will it have to be in the codebehind on some event in the parent repeater?

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• LINQ-to-SQL: How can I prevent 'objects you are adding to the designer use a different data connecti

  - by Timothy Khouri

  I am using Visual Studio 2010, and I have a LINQ-to-SQL DBML file that my colleagues and I are using for this project. We have a connection string in the web.config file that the DBML is using. However, when I drag a new table from my "Server Explorer" onto the DBML file... I get presented with a dialog that demands that do one of these two options: Allow visual studio to change the connection string to match the one in my solution explorer. Cancel the operation (meaning, I don't get my table). I don't really care too much about the debate as why the PMs/devs who made this tool didn't allow a third option - "Create the object anyway - don't worry, I'm a developer!" What I am thinking would be a good solution is if I can create a connection in the Server Explorer - WITHOUT A WIZARD. If I can just paste a connection string, that would be awesome! Because then the DBML designer won't freak out on me :O) If anyone knows the answer to this question, or how to do the above, please lemme know!

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• Can someone help me refactor this C# linq business logic for efficiency?

  - by Russell

  I feel like this is not a very efficient way of using linq. I was hoping somebody on here would have a suggestion for a refactor. I realize this code is not very pretty, as I was in a complete rush. public class Workflow { public void AssignForms() { using (var cntx = new ProjectBusiness.Providers.ProjectDataContext()) { var emplist = (from e in cntx.vw_EmployeeTaskLists where e.OwnerEmployeeID == null select e).ToList(); foreach (var emp in emplist) { // if employee has a form assigned: break; if (emp.GRADE > 15 || (emp.Pay_Plan.ToLower().Contains("al") || emp.Pay_Plan.ToLower().Contains("ex"))) { //Assign278(); } else if ((emp.Series.Contains("0905") || emp.Series.Contains("0511") || emp.Series.Contains("0110") || emp.Series.Contains("1801")) || (emp.GRADE >= 12 && emp.GRADE <= 15)) { var emptask = new ProjectBusiness.Providers.EmployeeTask(); emptask.TimespanID = cntx.Timespans.SingleOrDefault(t => t.BeginDate.Year == DateTime.Today.Year & t.EndDate.Year == DateTime.Today.Year).TimespanID; var FormID = (from f in cntx.Forms where f.FormName.Contains("450") select f.FormID).FirstOrDefault(); var TaskStatusID = (from s in cntx.TaskStatus where s.StatusDescription.ToLower() == "not started" select s.TaskStatusID).FirstOrDefault(); Assign450((int)emp.EmployeeID, FormID, TaskStatusID, emptask); cntx.EmployeeTasks.InsertOnSubmit(emptask); } else { //Assign185(); } } cntx.SubmitChanges(); } } private void Assign450(int EmployeeID, int FormID, int TaskStatusID, ProjectBusiness.Providers.EmployeeTask emptask) { emptask.FormID = FormID; emptask.OwnerEmployeeID = EmployeeID; emptask.AssignedToEmployeeID = EmployeeID; emptask.TaskStatusID = TaskStatusID; emptask.DueDate = DateTime.Today; } }

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• Getting minimum - Min() - for DateTime column in a DataTable using LINQ to DataSets?

  - by Jay Stevens

  I need to get the minimum DateTime value of a column in a DataTable. The DataTable is generated dynamically from a CSV file, therefore I don't know the name of that column until runtime. Here is code I've got that doesn't work... private DateTime GetStartDateFromCSV(string inputFile, string date_attr) { EnumerableRowCollection<DataRow> table = CsvStreamReader.GetDataTableFromCSV(inputFile, "input", true).AsEnumerable(); DateTime dt = table.Select(record => record.Field<DateTime>(date_attr)).Min(); return dt; } The variable table is broken out just for clarity. I basically need to find the minimum value as a DateTime for one of the columns (to be chosen at runtime and represented by date_attr). I have tried several solutions from SO (most deal with known columns and/or non-DateTime fields). What I've got throws an error at runtime telling me that it can't do the DateTime conversion (that seems to be a problem with Linq?) I've confirmed that the data for the column name that is in the string date_attr is a date value.

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• How can I get this dynamic WHERE statement in my LINQ-to-XML to work?

  - by Edward Tanguay

  In this question Jon Skeet offered a very interesting solution to making a LINQ-to-XML statement dynamic, but my knowledge of lambdas and delegates is not yet advanced enough to implement it: I've got it this far, but of course I get the error "smartForm does not exist in the current context": private void LoadWithId(int id) { XDocument xmlDoc = null; try { xmlDoc = XDocument.Load(FullXmlDataStorePathAndFileName); } catch (Exception ex) { throw new Exception(String.Format("Cannot load XML file: {0}", ex.Message)); } Func<XElement, bool> whereClause = (int)smartForm.Element("id") == id"; var smartForms = xmlDoc.Descendants("smartForm") .Where(whereClause) .Select(smartForm => new SmartForm { Id = (int)smartForm.Element("id"), WhenCreated = (DateTime)smartForm.Element("whenCreated"), ItemOwner = smartForm.Element("itemOwner").Value, PublishStatus = smartForm.Element("publishStatus").Value, CorrectionOfId = (int)smartForm.Element("correctionOfId"), IdCode = smartForm.Element("idCode").Value, Title = smartForm.Element("title").Value, Description = smartForm.Element("description").Value, LabelWidth = (int)smartForm.Element("labelWidth") }); foreach (SmartForm smartForm in smartForms) { _collection.Add(smartForm); } } Ideally I want to be able to just say: var smartForms = GetSmartForms(smartForm=> (int) smartForm.Element("DisplayOrder").Value > 50); I've got it this far, but I'm just not grokking the lambda magic, how do I do this? public List<SmartForm> GetSmartForms(XDocument xmlDoc, XElement whereClause) { var smartForms = xmlDoc.Descendants("smartForm") .Where(whereClause) .Select(smartForm => new SmartForm { Id = (int)smartForm.Element("id"), WhenCreated = (DateTime)smartForm.Element("whenCreated"), ItemOwner = smartForm.Element("itemOwner").Value, PublishStatus = smartForm.Element("publishStatus").Value, CorrectionOfId = (int)smartForm.Element("correctionOfId"), IdCode = smartForm.Element("idCode").Value, Title = smartForm.Element("title").Value, Description = smartForm.Element("description").Value, LabelWidth = (int)smartForm.Element("labelWidth") }); }

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• Automatic .NET code, nhibernate session, and LINQ datacontext clean-up?

  - by AverageJoe719

  Hi all, in my goal to adopt better coding practices I have a few questions in general about automatic handling of code. I have heard different answers both from online and talking with other developers/programmers at my work. I am not sure if I should have split them into 3 questions, but they all seem sort of related: 1) How does .NET handle instances of classes and other code things that take up memory? I recently found out about using the factory pattern for certain things like service classes so that they are only instantiated once in the entire application, but then I was told that '.NET handles a lot of that stuff automatically when mentioning it.' 2) How does Nhibernate's session handle automatic clean-up of un-used things? I've seen some say that it is great at handling things automatically and you should just use a session factory and that's it, no need to close it. But I have also read and seem many examples where people close the hibernate session. 3) How does LINQ's datacontext handle this? Most of the time I never .disposed my datacontext's and the app didn't see to take a performance hit (though I am not running anything super intensively), but it seems like most people recommend disposing of your datacontext after you are done with it. However, I have seen many many code examples where the dispose method is never called. Also in general I found it kind of annoying that you couldn't access even one-deep child related objects after disposing of the datacontext unless you explicity also grabbed them in the query. Thanks all. I am loving this site so far, I kind of get lost and spend hours just reading things on here. =)

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• How best to calculate derived currency rate conversions using C#/LINQ?

  - by chillitom

  class FxRate { string Base { get; set; } string Target { get; set; } double Rate { get; set; } } private IList<FxRate> rates = new List<FxRate> { new FxRate {Base = "EUR", Target = "USD", Rate = 1.3668}, new FxRate {Base = "GBP", Target = "USD", Rate = 1.5039}, new FxRate {Base = "USD", Target = "CHF", Rate = 1.0694}, new FxRate {Base = "CHF", Target = "SEK", Rate = 8.12} // ... }; Given a large yet incomplete list of exchange rates where all currencies appear at least once (either as a target or base currency): What algorithm would I use to be able to derive rates for exchanges that aren't directly listed? I'm looking for a general purpose algorithm of the form: public double Rate(string baseCode, string targetCode, double currency) { return ... } In the example above a derived rate would be GBP-CHF or EUR-SEK (which would require using the conversions for EUR-USD, USD-CHF, CHF-SEK) Whilst I know how to do the conversions by hand I'm looking for a tidy way (perhaps using LINQ) to perform these derived conversions perhaps involving multiple currency hops, what's the nicest way to go about this?

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• How to Get Dictionary<int, string> from Linq to XML Anonymous Object?

  - by DaveDev

  Currently I'm getting a list of HeaderColumns from the following XML snippet: <HeaderColumns> <column performanceId="12" text="Over last month %" /> <column performanceId="13" text="Over last 3 months %" /> <column performanceId="16" text="1 Year %" /> <column performanceId="18" text="3 Years % p.a." /> <column performanceId="20" text="5 Years % p.a." /> <column performanceId="22" text="10 Years % p.a." /> </HeaderColumns> from which I create an object as follows: (admitedly similar to an earlier question!) var performancePanels = new { Panels = (from panel in doc.Elements("PerformancePanel") select new { HeaderColumns = (from column in panel.Elements("HeaderColumns").Elements("column") select new { PerformanceId = (int)column.Attribute("performanceId"), Text = (string)column.Attribute("text") }).ToList(), }).ToList() }; I'd like if HeaderColumns was a Dictionary() so later I extract the values from the anonymous object like follows: Dictionary<int, string> myHeaders = new Dictionary<int, string>(); foreach (var column in performancePanels.Panels[0].HeaderColumns) { myHeaders.Add(column.PerformanceId, column.Text); } I thought I could achieve this with the Linq to XML with something similar to this HeaderColumns = (from column in panel.Elements("HeaderColumns").Elements("column") select new Dictionary<int, string>() { (int)column.Attribute("performanceId"), (string)column.Attribute("text") }).ToDictionary<int,string>(), but this doesn't work because ToDictionary() needs a Func parameter and I don't know what that is / how to implement it, and the code's probably wrong anyway! Could somebody please suggest how I can achieve the result I need? Thanks.

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• How to compare dictonary key with xml attribute value in xml using LINQ in c #?

  - by Pramodh

  Dear all, i've a dictonary " dictSample " which contains 1 data1 2 data2 3 data3 4 data4 and an xml file"sample.xml" in the form of: <node> <element id="1" value="val1"/> <element id="2" value="val2"/> <element id="3" value="val3"/> <element id="4" value="val4"/> <element id="5" value="val5"/> <element id="6" value="val6"/> <element id="7" value="val7"/> </node> i need to match the dictonary keys with the xml attribute id and to insert the matching id and the value of attribute"value" into another dictonary now i'm using like: XmlDocument XDOC = new XmlDocument(); XDOC.Load("Sample.xml"); XmlNodeList NodeList = XDOC.SelectNodes("//element"); Dictionary<string, string> dictTwo = new Dictionary<string, string>(); foreach (string l_strIndex in dictSample .Keys) { foreach (XmlNode XNode in NodeList) { XmlElement XEle = (XmlElement)XNode; if (dictSample[l_strIndex] == XEle.GetAttribute("id")) dictTwo.Add(dictSample[l_strIndex], XEle.GetAttribute("value").ToString()); } } please help me to do this in a simple way using LINQ

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• Is there an efficient way in LINQ to use a contains match if and only if there is no exact match?

  - by Peter

  I have an application where I am taking a large number of 'product names' input by a user and retrieving some information about each product. The problem is, the user may input a partial name or even a wrong name, so I want to return the closest matches for further selection. Essentially if product name A exactly matches a record, return that, otherwise return any contains matches. Otherwise return null. I have done this with three separate statements, and I was wondering if there was a more efficient way to do this. I am using LINQ to EF, but I materialize the products to a list first for performance reasons. productNames is a List of product names (input by the user). products is a List of product 'records' var directMatches = (from s in productNames join p in products on s.ToLower() equals p.name.ToLower() into result from r in result.DefaultIfEmpty() select new {Key = s, Product = r}); var containsMatches = (from d in directMatches from p in products where d.Product == null && p.name.ToLower().Contains(d.Key) select new { d.Key, Product = p }); var matches = from d in directMatches join c in containsMatches on d.Key equals c.Key into result from r in result.DefaultIfEmpty() select new {d.Key, Product = d.Product ?? (r != null ? r.Product: null) };

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• Are ternary operators not valid for linq-to-sql queries?

  - by KallDrexx

  I am trying to display a nullable date time in my JSON response. In my MVC Controller I am running the following query: var requests = (from r in _context.TestRequests where r.scheduled_time == null && r.TestRequestRuns.Count > 0 select new { id = r.id, name = r.name, start = DateAndTimeDisplayString(r.TestRequestRuns.First().start_dt), end = r.TestRequestRuns.First().end_dt.HasValue ? DateAndTimeDisplayString(r.TestRequestRuns.First().end_dt.Value) : string.Empty }); When I run requests.ToArray() I get the following exception: Could not translate expression ' Table(TestRequest) .Where(r => ((r.scheduled_time == null) AndAlso (r.TestRequestRuns.Count > 0))) .Select(r => new <>f__AnonymousType18`4(id = r.id, name = r.name, start = value(QAWebTools.Controllers.TestRequestsController). DateAndTimeDisplayString(r.TestRequestRuns.First().start_dt), end = IIF(r.TestRequestRuns.First().end_dt.HasValue, value(QAWebTools.Controllers.TestRequestsController). DateAndTimeDisplayString(r.TestRequestRuns.First().end_dt.Value), Invoke(value(System.Func`1[System.String])))))' into SQL and could not treat it as a local expression. If I comment out the end = line, everything seems to run correctly, so it doesn't seem to be the use of my local DateAndTimeDisplayString method, so the only thing I can think of is Linq to Sql doesn't like Ternary operators? I think I've used ternary operators before, but I can't remember if I did it in this code base or another code base (that uses EF4 instead of L2S). Is this true, or am I missing some other issue?

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• Iteration over a linq to sql query is very slow.

  - by devzero

  I have a view, AdvertView in my database, this view is a simple join between some tables (advert, customer, properties). Then I have a simple linq query to fetch all adverts for a customer: public IEnumerable<AdvertView> GetAdvertForCustomerID(int customerID) { var advertList = from advert in _dbContext.AdvertViews where advert.Customer_ID.Equals(customerID) select advert; return advertList; } I then wish to map this to modelItems for my MVC application: public List<AdvertModelItem> GetAdvertsByCustomer(int customerId) { List<AdvertModelItem> lstAdverts = new List<AdvertModelItem>(); List<AdvertView> adViews = _dataHandler.GetAdvertForCustomerID(customerId).ToList(); foreach(AdvertView adView in adViews) { lstAdverts.Add(_advertMapper.MapToModelClass(adView)); } return lstAdverts; } I was expecting to have some performance issues with the SQL, but the problem seems to be with the .ToList() function. I'm using ANTS performance profiler and it reports that the total runtime of the function is 1.400ms, and 850 of those is with the ToList(). So my question is, why does the tolist function take such a long time here?

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• What is the difference between these two linq implementations?

  - by Mahesh Velaga

  I was going through Jon Skeet's Reimplemnting Linq to Objects series. In the implementation of where article, I found the following snippets, but I don't get what is the advantage that we are gettting by splitting the original method into two. Original Method: // Naive validation - broken! public static IEnumerable<TSource> Where<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { if (source == null) { throw new ArgumentNullException("source"); } if (predicate == null) { throw new ArgumentNullException("predicate"); } foreach (TSource item in source) { if (predicate(item)) { yield return item; } } } Refactored Method: public static IEnumerable<TSource> Where<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { if (source == null) { throw new ArgumentNullException("source"); } if (predicate == null) { throw new ArgumentNullException("predicate"); } return WhereImpl(source, predicate); } private static IEnumerable<TSource> WhereImpl<TSource>( this IEnumerable<TSource> source, Func<TSource, bool> predicate) { foreach (TSource item in source) { if (predicate(item)) { yield return item; } } } Jon says - Its for eager validation and then defferring for the rest of the part. But, I don't get it. Could some one please explain it in a little more detail, whats the difference between these 2 functions and why will the validations be performed in one and not in the other eagerly? Conclusion/Solution: I got confused due to my lack of understanding on which functions are determined to be iterator-generators. I assumed that, it is based on signature of a method like IEnumerable<T>. But, based on the answers, now I get it, a method is an iterator-generator if it uses yield statements.

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• LINQ to XML - How to get Dictionary from Anonymous Object?

  - by DaveDev

  Currently I'm getting a list of HeaderColumns from the following XML snippet: <PerformancePanel> <HeaderColumns> <column performanceId="12" text="Over last month %" /> <column performanceId="13" text="Over last 3 months %" /> <column performanceId="16" text="1 Year %" /> <column performanceId="18" text="3 Years % p.a." /> <column performanceId="20" text="5 Years % p.a." /> <column performanceId="22" text="10 Years % p.a." /> </HeaderColumns> </PerformancePanel> from which I create an object as follows: (admitedly similar to an earlier question!) var performancePanels = new { Panels = (from panel in doc.Elements("PerformancePanel") select new { HeaderColumns = (from column in panel.Elements("HeaderColumns").Elements("column") select new { PerformanceId = (int)column.Attribute("performanceId"), Text = (string)column.Attribute("text") }).ToList(), }).ToList() }; I'd like if HeaderColumns was a Dictionary() so later I extract the values from the anonymous object like follows: Dictionary<int, string> myHeaders = new Dictionary<int, string>(); foreach (var column in performancePanels.Panels[0].HeaderColumns) { myHeaders.Add(column.PerformanceId, column.Text); } I thought I could achieve this with the Linq to XML with something similar to this HeaderColumns = (from column in panel.Elements("HeaderColumns").Elements("column") select new Dictionary<int, string>() { (int)column.Attribute("performanceId"), (string)column.Attribute("text") }).ToDictionary<int,string>(), but this doesn't work because ToDictionary() needs a Func parameter and I don't know what that is / how to implement it, and the code's probably wrong anyway! Could somebody please suggest how I can achieve the result I need? Thanks.

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• Does breaking chained Select()s in LINQ to objects hurt performance?

  - by Justin

  Take the following pseudo C# code: using System; using System.Data; using System.Linq; using System.Collections.Generic; public IEnumerable<IDataRecord> GetRecords(string sql) { // DB logic goes here } public IEnumerable<IEmployer> Employers() { string sql = "select EmployerID from employer"; var ids = GetRecords(sql).Select(record => (record["EmployerID"] as int?) ?? 0); return ids.Select(employerID => new Employer(employerID) as IEmployer); } Would it be faster if the two Select() calls were combined? Is there an extra iteration in the code above? Is the following code faster? public IEnumerable<IEmployer> Employers() { string sql = "select EmployerID from employer"; return Query.Records(sql).Select(record => new Employer((record["EmployerID"] as int?) ?? 0) as IEmployer); } I think the first example is more readable if there is no difference in performance.

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• If I cast an IQueryable as an IEnumerable then call a Linq extension method, which implementation gets called?

  - by James Morcom

  Considering the following code: IQueryable<T> queryable; // something to instantiate queryable var enumerable = (IEnumerable<T>) queryable; var filtered = enumerable.Where(i => i > 3); In the final line, which extension method gets called? Is it IEnumerable<T>.Where(...)? Or will IQueryable<T>.Where(...) be called because the actual implementation is still obviously a queryable? Presumably the ideal would be for the IQueryable version to be called, in the same way that normal polymorphism will always use the more specific override. In Visual Studio though when I right-click on the Where method and "Go to Definition" I'm taken to the IEnumerable version, which kind of makes sense from a visual point-of-view. My main concern is that if somewhere in my app I use Linq to NHibernate to get a Queryable, but I pass it around using an interface that uses the more general IEnumerable signature, I'll lose the wonders of deferred database execution!

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• Mongodb, linq driver. How to construct Contains with variable or statements

  - by Syska

  I'm using the LINQ Driver for C#, works great. Sorting a lot of properties but heres a problem I can't solve, its probebly simple. var identifierList = new []{"10", "20", "30"}; var newList = list.Where(x => identifierList.Contains(x.Identifier)); This is NOT supported ... So I could do something like: var newList = list.Where(x => x.Identifier == "10" || x.Identifier == "20" || x.Identifier == "30"); But since the list is variable ... how do I construct the above? Or are there even better alternatives? The list is of type IQueryable<MyCustomClass> For information ... this is used as a filter of alot of properties. In SQL I could have a parent - child relationship. But as I can't as the parent for the main ID I need to take all the ID's out and then construct it like this. Hopes this makes sense. If needed I will explain more.

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• How do I add two lists in Linq so addedList[x] = listOne[x] + listTwo[x]?

  - by Audie

  I want to add two lists of a numeric type such that addedList[x] = listOne[x] + listTwo[x] The output of the list needs to be a Generic.IEnumerable that I can use in future linq queries. While I was able to do it using the code below, I can't help but feel like there must be a better way. Any ideas? List<int> firstList = new List<int>(new int[] { 1, 3, 4, 2, 5, 7, 2, 5, 7, 8, 9, 0 }); List<int> secondList = new List<int>(new int[] { 4, 6, 8, 3, 1, 5, 9, 3, 0 }); int findex = 0; ILookup<int, int> flookup = firstList.ToLookup(f => { int i = findex; findex++; return i; }, p => p); var listsAdded = from grp in flookup select grp.First() + secondList.ElementAtOrDefault(grp.Key); foreach (int i in listsAdded) Console.WriteLine(i);

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• monit syntax error : "if 5 restarts within 5 cycles then alert"

  - by omry

  I am trying to get an alert from monit if it fails to restart a service 5 times, but I get a syntax error /etc/monit/monit.d/engine.conf:5: Error: syntax error 'alert' this is the engine.conf file: check process engine with pidfile /var/run/engine.pid group engine start program = "/etc/init.d/engine start" stop program = "/etc/init.d/engine stop" if 5 restarts within 5 cycles then alert any idea what's wrong with it?

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• Syntax error on running a batch file to replace files

  - by Ralph

  I have a batch file intended to replace all instances of tracking.js within a folder/sub folders. FOR /R "D:\Virtual Servers (Testing)\CourseWare Master\Shared\Jenison\Version1.2\" %%I IN (tracking.js*) DO COPY /Y "D:\Virtual Servers (Testing)\CourseWare Master\Shared\Jenison\tracking.js" %%~fI When this is run I get the following syntax error C:COPY /Y "D:\Virtual Servers (Testing)\CourseWare Master\Shared\Jenison\track ing.js" D:\Virtual Servers (Testing)\CourseWare Master\Shared\Jenison\Version1.2 \SHAPERS_COMBINED\Smarter Communications\WhatisInfluencing\script\Tracking.js The syntax of the command is incorrect. Ideas please?

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• display sql syntax in Oracle's sqlplus?

  - by user1375963

  What is in Oracle's sqlplus equivalent of Linux's man or --help ? When I'm in sqlplus and type help index, I get some commands displayed, but there is no way to get specific sql syntax. For example if I type 'help select' I get: SP2-0172 No HELP matching this tiopic was found. Of course, I would like to get all available options for select command. How can I get info or sql syntax while I'm at sql prompt ? Thanks

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