Value cannot be null Parameter name source

Question

This is probably the biggest waste of time problem I have spent hours on solving for a long time   var db   new hublisherEntities    establishment brands est   new establishment brands     est brand id   1  est establishment id   1  est price   collection  price    est size   collection  size     db establishment brands Add est   db SaveChanges      This gives me an error of     Value cannot be null  Parameter name  source   stacktrace of      ArgumentNullException  Value cannot be null  Parameter name  source     System Linq Enumerable Any IEnumerable1 source  Func2 predicate     4083335    System Data Entity Internal InternalContext WrapUpdateException UpdateException   updateException   87   System Data Entity Internal InternalContext SaveChanges    193   System Data Entity Internal LazyInternalContext SaveChanges    33   System Data Entity DbContext SaveChanges    20           I just want to add an entity to the table  The ORM is EF

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It could be as silly as in my case where savechanges was erroring bcoz the db did not have foreign keys and associations were added to EDM tables. I added foreign keys in the db and regenerated EDM for a fix.

The errors I was seeing are as follows: Case 1 -> when using DBContext for EDM Message=Value cannot be null. Parameter name: source at System.Linq.Enumerable.Any[TSource](IEnumerable1 source, Func2 predicate)

Case 2 -> when using ObjectContext for EDM Message=Unable to update the EntitySet 'Contact' because it has a DefiningQuery and no element exists in the element to support the current operation.

(Just wanted to throw it in there in case it helps someone).

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In my case  the problem popped up while configuring the web application on IIS  When the update command on any record was fired this error got generated    It was a permission issue on App Data which set to read-only  Right-click the folder  uncheck the Read-only checkbox and you are done  By the way  for testing purpose  I was using the localdb database which was in App Data folder

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In MVC  View screen is calling method which is in Controller or Repository cs and assigning return value to any control in CSHTML but that method is actually not implemented in  cs controller  then CSHTML will throw the NULL parameter exception

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Resolved with the following solution   Right click on the edmx file  select Open with  XML editor Locate the entity in the edmx StorageModels element Remove the DefiningQuery entirely Rename the store Schema  dbo  to Schema  dbo   if exists   Remove the store Name property

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Make sure you are injecting the repository into the service s constructor   That solved it for me     smacks forehead

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In case anyone else ends up here with my issue with a DB First Entity Framework setup   Long story short  I needed to overload the Entities constructor to accept a connection string  the reason being the ability to use Asp Net Core dependency injection container pulling the connection string from appsettings json  rather than magically getting it from the App config file when calling the parameterless constructor   I forgot to add the calls to initialize my DbSets in the new overload  So the auto-generated parameter-less constructor looked something like this       public MyEntities             base  name MyEntity                 Set1   Set lt MyDbSet1 gt             Set2   Set lt MyDbSet2 gt             And my new overload looked like this       public MyEntities string connectionString            base connectionString                The solution was to add those initializers that the auto-generated code takes care of  a simple missed step        public MyEntities string connectionString            base connectionString                Set1   Set lt MyDbSet1 gt             Set2   Set lt MyDbSet2 gt             This really threw me for a loop because some calls in our Respository that used the DbContext worked fine  the ones that didn t need those initialized DBSets   and the others throw the runtime error described in the OP

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I got this error when I had an invalid Type for an entity property   public Type ObjectType  get set     When I removed the property the error stopped occurring

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I had this one a while back  and the answer isn t necessarily what you d expect  This error message often crops up when your connection string is wrong   At a guess  you ll need something like this    lt connectionStrings gt       lt add name  hublisherEntities  connectionString  Data Source localhost Initial Catalog hublisher Integrated Security True   providerName  System Data SqlClient    gt   lt  connectionStrings gt   lt entityFramework gt       lt defaultConnectionFactory type  System Data Entity Infrastructure LocalDbConnectionFactory  EntityFramework  gt           lt parameters gt               lt parameter value  Data Source localhost Initial Catalog hublisher Integrated Security True    gt           lt  parameters gt       lt  defaultConnectionFactory gt   lt  entityFramework gt    What s happening is that it s looking for a data source in the wrong place  Entity Framework specifies it slightly differently  If you post your connection string and EF config then we can check

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I just got this exact error in  Net Core 2 2 Entity Framework because I didn t have the set  in my DbContext like so   public DbSet lt Account gt  Account   get      changed to   public DbSet lt Account gt  Account   get  set     However  it didn t show the exception until I tried to use a linq query with Where   and Select   as others had mentioned above   I was trying to set the DbSet as read only  I ll keep trying

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My reason was different to the rest here so I thought I d post it for anyone else who might have this issue   I was calling Count on an instance of DbSet with a filter of null i e   dbSet Count null     I found that passing null here was causing the error so I now call the parameter-less method if the filter is null    if  filter    null          return dbSet Count        else         return dbSet Count filter        This sorted the issue for me   This may be an issue for any other methods on DbSet as well

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And  in my case  I mistakenly define my two different columns as identities on DbContext configurations like below  builder HasKey e   gt  e HistoryId  HasName  quot HistoryId quot    builder Property e   gt  e Id  UseSqlServerIdentityColumn      History Id should use identity column in this example  When I correct it like below  builder HasKey e   gt  e HistoryId  HasName  quot HistoryId quot    builder Property e   gt  e HistoryId  UseSqlServerIdentityColumn     I have also got rid of this error

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Somewhere inside the DbContext is a value that is IEnumerable and is queried with Any    or Where   or Select   or any other LINQ-method   but this value is null   Find out if you put a query together  somewhere outside your example code  where you are using a LINQ-method  or that you used an IEnumerable as a parameter which is NULL

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Take a Row in the database and make all the column null in that row like this  NULL  Now pass that NULL value using try catch or if else

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My mistake was forgetting to add the  ThenInclude s    s SubChildEntities  onto the parent  Include c    c SubChildEntities  to the Controller action when attempting to call the SubChildEntities in the Razor view   var  lt parent gt    await  context Parent              Include c   gt  c  lt ChildEntities gt                ThenInclude s   gt  s  lt SubChildEntities gt                SingleOrDefaultAsync m   gt  m Id    id     It should be noted that Visual Studio 2017 Community s IntelliSense doesn t pick up the SubChildEntities object in the lambda expression in the  ThenInclude    It does successfully compile and execute though

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Using the  Count   without checking for null is one strong reason for this error  THE FIX  if someList    null  amp  someList Count   gt 0          Now  put your hackable code here

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just as an FYI  somebody may find it useful  I was chasing my tail for this error almost 2 days and was always thinking something big and looking for the classes that might be the issue and finally i found it very stupid issue and it was in my mark up  HTML  code in mypage ascx  the issue was I have a  lt asp EntityDataSource gt  and this has got a include property and I have some other tables listed here and mistakenly a table was there that has been delete from the database recently and I never noticed and it returning null with other entities  I just removed the stupid table from the include list and I am good to go  hope this can help somebody

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I know this is a long way from the year 2013 of the question  but this symptom can show up if you don t have lazy loading enabled when migrating an ASP NET 5 app to ASP NET Core  and then trying to upgrade to Entity Framework Core 2 x  from EF 6   Entity Framework Core has moved lazy loading proxy support to a separate package  so you have to install it   This is particularly true if all you have loaded is an Entity Framework Core Sql Server package  which turns on Entity Framework just fine    After installing the proxies package  then  as the docs say  invoke  UseLazyLoadingProxies   on the DbContext options builder  in your Startup DI setup section  or wherever you configure your DbContext   and the navigational property that was throwing the above exception will stop throwing it  and will work as Entity Framework 6 used to

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I had the same issue with XUnit  The problem was with my database connection  Check your connection string is correct or not

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This exception will be returned if you attempt to count values in a null collection   For example the below works when Errors is not null  however if Errors is null then the Value cannot be null  Parameter name  source exception occurs   if  graphQLResponse Errors Count    gt  0    This exception can be avoided by checking for null instead   if  graphQLResponse Errors    null

[c#] Value cannot be null. Parameter name: source

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