c# - Value cannot be null. Parameter name: source

c# – Value cannot be null. Parameter name: source

c# – Value cannot be null. Parameter name: source

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.

I had this one a while back, and the answer isnt necessarily what youd expect. This error message often crops up when your connection string is wrong.

At a guess, youll need something like this:

<connectionStrings>
    <add name=hublisherEntities connectionString=Data Source=localhost;Initial Catalog=hublisher;Integrated Security=True; providerName=System.Data.SqlClient />
</connectionStrings>
<entityFramework>
    <defaultConnectionFactory type=System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework>
        <parameters>
            <parameter value=Data Source=localhost;Initial Catalog=hublisher;Integrated Security=True />
        </parameters>
    </defaultConnectionFactory>
</entityFramework>

Whats happening is that its 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.

c# – Value cannot be null. Parameter name: source

I just got this exact error in .Net Core 2.2 Entity Framework because I didnt have the set; in my DbContext like so:

public DbSet<Account> Account { get; }

changed to:

public DbSet<Account> Account { get; set;}

However, it didnt 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. Ill keep trying…

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