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POCode First to existing database - setting up a one to one relationship where TableA doesn't have an approprite foreign key reference to TableB
 

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  1. POCode First to existing database - setting up a one to one relationship where TableA doesn't have an approprite foreign key reference to TableB
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    <p>Ok, I have a strange situation while trying to map some POCO classes to a database that was not created by me.</p> <p>Here is the setup of the tables.</p> <pre><code>TableA ( TableA_ID int primary key, // other fields ) TableB ( TableB_ID int primary key, TableA_ID int unique not null, // other fields ) </code></pre> <p>So, how the tables are supposed to work together is that TableB has a reference to TableA - and it is a 1 to 1 relationship. TableA however does not have a foreign key to TableB's primary key.</p> <p>I can obviously set up the following relationships</p> <pre><code>public class TableA { public int TableA_ID { get; set; } public virtual ICollection&lt;TableB&gt; TableBs { get; set; } } public class TableB { public int TableB_ID { get; set; } public int TableA_ID { get; set; } public virtual TableA TableA { get; set; } } </code></pre> <p>With this setup I can say - this and it works ok:</p> <pre><code>TableA.TableBs.FirstOrDefault().SomeField; </code></pre> <p>But, what I really want is this</p> <pre><code>public class TableA { public int TableA_ID { get; set; } public virtual TableB TableB { get; set; } } public class TableB { public int TableB_ID { get; set; } public int TableA_ID { get; set; } public virtual TableA TableA { get; set; } } </code></pre> <p>With this setup I could then say:</p> <pre><code>TableA.TableB.SomeField; </code></pre> <p>Is there any way to map the TableA_ID from TableA to the TableA_ID from TableB to make the TableA class work how I want?</p>
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    1. USSean Hosey
    1. USSean Hosey
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    1. COEntity Framework does not support unique keys, sorry. You could *mostly* get this working by modelling this as `public class TableA { public virtual ICollection<TableB> TableBs { get; set; } }` and making sure never to map more than one `TableB` to the same `TableA`, but you would get stuck with modifications: there is no way to ensure that *during* `SaveChanges`, modifications get sent to the database in the right order, so that's really a non-answer.
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      1. POCode First to existing database - setting up a one to one relationship where TableA doesn't have an approprite foreign key reference to TableB
      1. UShvd
    2. COYes, I have modified my question to reflect this - and that is exactly what I am doing right now. But, I wanted to stop having to say TableA.TableBs.FirstOrDefault().SomeField; and instead be able to say TableA.TableB.SomeField; As for the SaveChanges - thats ok - because - for my purposes - I will be accessing this data as read-only.
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      1. POCode First to existing database - setting up a one to one relationship where TableA doesn't have an approprite foreign key reference to TableB
      1. USSean Hosey
 

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