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  • LINQ query checks for null

    - by user300992
    I have a userList, some users don't have a name (null). If I run the first LINQ query, I got an error saying "object reference not set to an instance of an object" error. var temp = (from a in userList where ((a.name == "john") && (a.name != null)) select a).ToList(); However, if I switch the order by putting the checking for null in front, then it works without throwing any error: var temp = (from a in userList where ((a.name != null) && (a.name == "john")) select a).ToList(); Why is that? If that's pure C# code (not LINQ), I think both would be the same. I don't have SQL profiler, I am just curious what will be the difference when they are being translated on SQL level.

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  • Asp.Net MVC - Plugins Directory, Community etc?

    - by Jörg Battermann
    Good evening everyone, I am currently starting to dive into asp.net mvc and I really like what I see so far.. BUT I am somewhat confused about 'drop-in' functionality (similiar to what rails and it's plugins and nowadays gems are), an active community to contact etc. For rails there's github with one massiv index of plugins/gems/code-examples regarding mostly rails (despite their goal being generic source-code hosting..), for blogs, mailing lists etc it's also pretty easy to find the places the other developers flock around, but... for asp.net mvc I am somewhat lost where to go/look. It all seems scattered across codeplex and private sites, google code hosting etc etc.. but is there one (or few places) where to turn to regarding asp.net mvc development, sample code etc? Cheers and thanks, -Jörg

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  • showing null rows using join

    - by Pradyut Bhattacharya
    Hi, In mysql i m selecting from a table shouts having a foreign key to another table named "roleuser" with the matching column as user_id Now the user_id column in the shouts table for some rows is null (not actually null but with no inserts in mysql) How to show all the rows of the shouts table either with user_id null or not I m executing the sql statement SELECT s.*, r.firstname, r.lastname FROM shouts s left join roleuser r where r.user_id = s.user_id limit 50; which does not executes and shows You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'where r.user_id = s.user_id limit 50' at line 2 but using inner join the sql executes which shows rows which only have user_id values in the shouts table. the nulls are not shown. SELECT s.*, r.firstname, r.lastname FROM shouts s inner join roleuser r where r.user_id = s.user_id limit 50; How can i show all the rows from the shouts table and null values in the firstname and lastname columns where the user_id is null in the shouts table. If not at all possible with sql may be using stored procedures... Thanks Pradyut

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  • Does NULL and nil are equal?

    - by monish
    Hi Guys, Actually my question here is does Null and nil are equal or not? I had an Example but I am confused when they are equal when they are not. NSNull *nullValue = [NSNull null]; NSArray *arrayWithNull = [NSArray arrayWithObject:nullValue]; NSLog(@"arrayWithNull: %@", arrayWithNull); id aValue = [arrayWithNull objectAtIndex:0]; if (aValue == nil) { NSLog(@"equals nil"); } else if (aValue == [NSNull null]) { NSLog(@"equals NSNull instance"); if ([aValue isEqual:nil]) { NSLog(@"isEqual:nil"); } } Here in the above case it shows that both Null and nil are not equal and it displays "equals NSNull instance" NSString *str=NULL; id str1=nil; if(str1 == str) { printf("\n IS EQUAL........"); } else { printf("\n NOT EQUAL........"); } And in the second case it shows both are equal and it displays "IS EQUAL". Anyone's help will be much appreciated. Thank you, Monish.

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  • Null Pointer Exception while using Java Compiler API

    - by java_geek
    MyClass.java: package test; public class MyClass { public void myMethod(){ System.out.println("My Method Called"); } } Listing for SimpleCompileTest.java that compiles the MyClass.java file. SimpleCompileTest.java: package test; import javax.tools.*; public class SimpleCompileTest { public static void main(String[] args) { String fileToCompile = "test" + java.io.File.separator +"MyClass.java"; JavaCompiler compiler = ToolProvider.getSystemJavaCompiler(); int compilationResult = compiler.run(null, null, null, fileToCompile); if(compilationResult == 0){ System.out.println("Compilation is successful"); }else{ System.out.println("Compilation Failed"); } } } I am executing the SimpleCompileTest class and getting a NullPointerException. The ToolProvider.getSystemJavaCompiler() is returning null. Can someone tell me what is wrong with the code

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  • select rows with column that is not null?

    - by fayer
    by default i have one column in mysql table to be NULL. i want to select some rows but only if the field value in that column is not NULL. what is the correct way of typing it? $query = "SELECT * FROM names WHERE id = '$id' AND name != NULL"; is this correct?

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  • redirectToAction results in null model

    - by Maslow
    I have 2 actions on a controller: public class CalculatorsController : Controller { // // GET: /Calculators/ public ActionResult Index() { return RedirectToAction("Accounting"); } public ActionResult Accounting() { var combatants = Models.Persistence.InMemoryCombatantPersistence.GetCombatants(); Debug.Assert(combatants != null); var bvm = new BalanceViewModel(combatants); Debug.Assert(bvm!=null); Debug.Assert(bvm.Combatants != null); return View(bvm); } } When the Index method is called, I get a null model coming out. When the Accounting method is called directly via it's url, I get a hydrated model.

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  • iPad/iPhone: Form filling application pointers

    - by raj.tiwari
    Folks, I am starting work on an iPad/iPhone application that is essentially a form-filing UI. The requirement is to present a (rather large) form to the user. The form is composed of sections and questions, like so: Form Question 0.1 Question 0.2 Section 1 Question 1.1 etc. The user can take various paths down the form based on answers to questions. I would like to architect this by defining a declarative markup that can be used to author the form questionnaire including traversal rules. My questions are: Can anyone recommend a markup/language that would satisfy the declaration requirement? Is there any existing library that would ease the implementation as described above? Thanks for your time.

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  • not including null values in sql join

    - by Ashanti
    Hi, I have two tables CustomerAddress(CustomerId, City, Country) and CustomerTransactions(TransactionId, CustomerId, CustomerContact). Here are the values in the tables: For CustomerAddress: 1001, El Paso, USA 1002, Paris, France 1003, Essen, Germany For CustomerTransactions: 98, 1001, Phillip 99, 1001, NULL 100, 1001, NULL 101, 1003, Carmen 102, 1003, Carmen 103, 1003, Lola 104, 1003, NULL 105, 1002, NULL I'm trying to join both tables and have the following result set: 1001, El Paso, USA, Phillip 1002, Paris, France, (empty string) 1003, Essen, Germany, Carmen 1003, Essen, Germany, Lola It seems like a simple join but I'm having trouble coming up with the above result set. Please help. Thanks.

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  • Why does GetClusterShape return null when the cluster specification was retrieved through the GetClu

    - by Markus Olsson
    Suppose I have a virtual earth shape layer called shapeLayer1 (my creative energy is apparently at an alltime low). When i call the GetClusteredShapes method I get an array of VEClusterSpecification objects that represent each and every one of my currently visible clusters; no problem there. But when I call the GetClusterShape() method it returns null... null! Why on earth would it do that? I used firebug to confirm that the private variable of the VEClusterSpecification that's supposed to hold a reference to the shape is indeed null so it's not the method that's causing the problem. Some have suggested that this is actually documented behavior Returns null if a VEClusterSpecification object was returned from the VEShapeLayer.GetClusteredShapes Method But looking at the current MSDN documentation for the VEShape class it says: Returns if a VEClusterSpecification object was returned from the VEShapeLayer.GetClusteredShapes Method Is this a bug or a feature? Is there any known workarounds or (if it is a bug) some plan on when they are going to fix it?

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  • NULL-keys for key/value table

    - by user72185
    (Using Oracle) I have a table with key/value pairs like this: create table MESSAGE_INDEX ( KEY VARCHAR2(256) not null, VALUE VARCHAR2(4000) not null, MESSAGE_ID NUMBER not null ) I now want to find all the messages where key = 'someKey' and value is 'val1', 'val2' or 'val3' - OR value is null in which case there will be no entry in the table at all. This is to save space; there would be a large number of keys with null values if I stored them all. I think this works: SELECT message_id FROM message_index idx WHERE ((key = 'someKey' AND value IN ('val1', 'val2', 'val3')) OR NOT EXISTS (SELECT 1 FROM message_index WHERE key = 'someKey' AND idx.message_id = message_id)) But is is extremely slow. Takes 8 seconds with 700K records in message_index and there will be many more records and more search criteria when moving outside of my test environment. Primary key is key, value, message_id: add constraint PK_KEY_VALUE primary key (KEY, VALUE, MESSAGE_ID) And I added another index for message_id, to speed up searching for missing keys: create index IDX_MESSAGE_ID on MESSAGE_INDEX (MESSAGE_ID) I will be doing several of these key/value lookups in every search, not just one as shown above. So far I am doing them nested, where output id's of one level is the input to the next. E.g.: SELECT message_id from message_index WHERE (key/value compare) AND message_id IN ( SELECT ... and so on ) What can I do to speed this up?

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  • JQuery and WCF - GET Method passes null

    - by user70192
    Hello, I have a WCF service that accepts requests from JQuery. Currently, I can access this service. However, the parameter value is always null. Here is my WCF Service definition: [OperationContract] [WebInvoke(Method = "GET", BodyStyle = WebMessageBodyStyle.WrappedRequest, RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json)] public string ExecuteQuery(string query) { // NOTE: I get here, but the query parameter is always null string results = Engine.ExecuteQuery(query); return results; } Here is my JQuery call: var searchUrl = "/services/myService.svc/ExecuteQuery"; var json = { "query": eval("\"test query\"") }; alert(json2string(json)); // Everything is correct here if (json != null) { $.ajax({ type: "GET", url: searchUrl, contentType: "application/json; charset=utf-8", data: json2string(json), dataType: "json" }); } What am I doing wrong? It seems odd that I can call the service but the parameter is always null. Thank you

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  • What's the difference between an option type and a nullable type?

    - by Peter Olson
    In F# mantra there seems to be a visceral avoidance of null, Nullable<T> and its ilk. In exchange, we are supposed to instead use option types. To be honest, I don't really see the difference. My understanding of the F# option type is that it allows you to specify a type which can contain any of its normal values, or None. For example, an Option<int> allows all of the values that an int can have, in addition to None. My understanding of the C# nullable types is that it allows you to specify a type which can contain any of its normal values, or null. For example, a Nullable<int> a.k.a int? allows all of the values that an int can have, in addition to null. What's the difference? Do some vocabulary replacement with Nullable and Option, null and None, and you basically have the same thing. What's all the fuss over null about?

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  • How can I set a field to null in a Pre-Update Plugin

    - by Juergen
    I developed a Pre-Update Plugin for the Case entity. In this plugin I want to set a string field to a new value. It works smoothly if the new value is not null. But if the new value si null, it is just ignored. This works: Incident caseTarget = ((Entity) localContext.PluginExecutionContext.InputParameters["Target"]).ToEntity<Incident>(); caseTarget.ProductSerialNumber = "new value"; After the execution of the plugin, the ProductSerialNumber field has value "new value". This doesn't work: Incident caseTarget = ((Entity) localContext.PluginExecutionContext.InputParameters["Target"]).ToEntity<Incident>(); caseTarget.ProductSerialNumber = null; After the execution of the plugin, the ProductSerialNumber field has still its old value. How can I set the target's field to null?

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  • Is passing NULL param exactly the same as passing no param

    - by park
    I'm working with a function whose signature looks like this afunc(string $p1, mixed $p2, array $p3 [, int $p4 = SOM_CONST [, string $p5 ]] ) In some cases I don't have data for the last parameter $p5 to pass, but for the sake of consistency I still want to pass something like NULL. So my question, does PHP treat passing a NULL exactly the same as not passing anything? somefunc($p1, $p2, $p3, $p4 = SOM_CONST); somefunc($p1, $p2, $p3, $p4 = SOM_CONST, NULL);

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  • MonoRail - How to grab records where a column isn't null

    - by Justin
    Hey, In MonoRail/Active Record if I want to grab all records that have a certain column equal to null, I can do: public static Category[] AllParentCategories() { return (FindAllByProperty("Parent.Id", null)); } However, what if I want to grab all records where that column doesn't equal null? I can't figure out how to do that using this FindAllByProperty method, is there another method that is more flexible or a way to grab records using a linq-like querying language? Thanks, Justin

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  • LINQ, Left Join, Only Get where null in join table

    - by kmehta
    Hi. I am trying to do a left outer join on two tables, but I only want to return the results from the first table where the second table does not have a record (null). var agencies = from a in agencyList join aa in joinTable on a.AgencyId equals aa.AgencyId into joined from aa in joined.DefaultIfEmpty() where aa == null) select a; But this does not exclude the non null values of aa, and returns all the records just the same as if the 'where aa == null' was not there. Any help is appreciated. Thanks.

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  • Constructor invocation returned null: what to do?

    - by strager
    I have code which looks like: private static DirectiveNode CreateInstance(Type nodeType, DirectiveInfo info) { var ctor = nodeType.GetConstructor(new[] { typeof(DirectiveInfo) }); if(ctor == null) { throw new MissingMethodException(nodeType.FullName, "ctor"); } var node = ctor.Invoke(new[] { info }) as DirectiveNode; if(node == null) { // ???; } return node; } I am looking for what to do (e.g. what type of exception to throw) when the Invoke method returns something which isn't a DirectiveNode or when it returns null (indicated by // ??? above). (By the method's contract, nodeType will always describe a subclass of DirectiveNode.) I am not sure when calling a constructor would return null, so I am not sure if I should handle anything at all, but I still want to be on the safe side and throw an exception if something goes wrong.

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  • about null values!

    - by user329820
    Hi I have a question that if we declare a variable and then do not set it explicitly to null value then it would be null outomatically ,i mean that the below code will return true or false ? thanks DECLARE @val CHAR(4) If @val = NULL

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  • Convert Null Value to String - C#.NET

    - by peace
    foreach (PropertyInfo PropertyItem in this.GetType().GetProperties()) { PropertyItem.SetValue(this, objDataTable.Rows[0][PropertyItem.Name.ToString()], null); } In one of the loops i get this exceptional error: Object of type 'System.DBNull' cannot be converted to type 'System.String'. The error occurs because one of the fields in the database has no value (null), so the string property could not handle it. How can i convert this null to string? I got this solution If you know a shorter or better one, feel free to post it. I'm trying to avoid checking on every loop is current value is null or not.

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  • Constructor invokation returned null: what to do?

    - by strager
    I have code which looks like: private static DirectiveNode CreateInstance(Type nodeType, DirectiveInfo info) { var ctor = nodeType.GetConstructor(new[] { typeof(DirectiveInfo) }); if(ctor == null) { throw new MissingMethodException(nodeType.FullName, "ctor"); } var node = ctor.Invoke(new[] { info }) as DirectiveNode; if(node == null) { // ???; } return node; } I am looking for what to do (e.g. what type of exception to throw) when the Invoke method returns something which isn't a DirectiveNode or when it returns null (indicated by // ??? above). (By the method's contract, nodeType will always describe a subclass of DirectiveNode.) I am not sure when calling a constructor would return null, so I am not sure if I should handle anything at all, but I still want to be on the safe side and throw an exception if something goes wrong.

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  • Bizarre WHERE col = NULL behavior

    - by Kenneth
    This is a problem one of our developers brought to me. He stumbled across an old stored procedure which used 'WHERE col = NULL' several times. When the stored procedure is executed it returns data. If the query inside the stored procedure is executed manually it will not return data unless the 'WHERE col = NULL' references are changed to 'WHERE col IS NULL'. Can anyone explain this behavior?

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