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POCode first add entity with many-to-many relationship
 

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    <p>I have an object Customer that can have multiple customer types and each customer type can have multiple customers. I'm new to EF but have managed to add a customer, but can't seem to get the syntax right for adding the customer's customer types as well.</p> <p>My customer class (simplified):</p> <pre><code>public partial class Customer { public virtual int Id { get; set;} public virtual string Name { get; set;} #region Navigation Properties public virtual ICollection&lt;CustomerType&gt; CustomerTypes { get; set; } #endregion } </code></pre> <p>Customer type:</p> <pre><code>public partial class CustomerType { public virtual int Id { get; set; } public virtual string Name { get; set; } #region Navigation Properties public virtual ICollection&lt;Customer&gt; Customers { get; set; } #endregion } </code></pre> <p>When I run this project a CustomerTypeCustomer table is created with columns Customer_Id and CustomerType_Id so this is fine.</p> <p>I then create the customer like so:</p> <pre><code>// code behind var customer = new Customer(); customer.name = txtCustomerName.Text; using (var context = new MyEntities()) { context.Customers.Add(customer); context.SaveChanges(); } </code></pre> <p>I had a look here <a href="https://stackoverflow.com/questions/4253165/insert-update-many-to-many-entity-framework-how-do-i-do-it">Insert/Update Many to Many Entity Framework . How do I do it?</a> and tried to do something similar with customer types:</p> <pre><code>var customer = new Customer(); customer.name = txtCustomerName.Text; // only starting with one customer type selected in a check box list CustomerType customerType = context.CustomerTypes.FirstOrDefault(i =&gt; i.Id == 1); using (var context = new MyEntities()) { // IncidentTypes throws Object reference not set to an instance of an object customer.CustomerTypes.add(customerType); context.Customers.Add(customer); context.SaveChanges(); } </code></pre> <p>Am I missing something obvious here?</p> <p>Thanks in advance.</p> <p>Edit: for some reason I only have .Add( no AddToObject, AttachTo etc.</p>
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A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

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