Need hep on code first.

Question

Hi all, i'm using EF 4.3. And Code First is really useful. However, i'm facing some problem which i can't figure out a solution.

I have a class OpCode and a class name SubOpCode as follows.

Basically, I have different set of OpCode and different set of SubOpCode. 

An OpCode contains a collection of SubCode associated with it.

Different OpCode can have the same set of same SubOpCode.

How can i achieve in code first? Many thanks!

public class SubOpCode
{
    public int Id { get; set; }
    public String CodeName { get; set; }
    public OpCode ParentOpCode { get; set }
}

public class OpCode
{
    public int Id { get; set;}
    public String CodeName { get; set; }
    public ICollection<SubOpCode> { get; }
}

Answer 1

Hi j3r;

It sounds like what you need is a Many to Many relationship. If you construct your model as follows it will do that.

public class SubOpCode
{
    public int SubOpCodeId { get; set; }
    public String CodeName { get; set; }

    public virtual ICollection<OpCode> OpCodes { get; set; }
}

public class OpCode
{
    public int OpCodeId { get; set;}
    public String CodeName { get; set; }

    public virtual ICollection<SubOpCode> SubOpCodes { get; set; }
}

public class Context : DbContext
{
    public DbSet<OpCode> OpCodes { get; set; }
    public DbSet<SubOpCode> SubOpCodes { get; set; }
}

In the database it will look like this:

 

---

Fernando (MCSD)

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Answer 2

Thanks for the help!! Another question..... hehe. How do i mark a field to be unique?

For example for class OpCode. I wan Id to retain and having CodeName to be unique for every row.

public class OpCode
{
    [Key]
    public int OpCodeId { get; set; }

    // How do i mark it to be unique?
    public String CodeName { get; set; }

    public virtual ICollection<OpCode> OpCodes { get; set; }
}

Answer 3

I'm facing some problems inserting data.

OpCode.Name and SubCode.Name should be unique for every entry and the Auto-generated table SubOpCodeOpCodesshould be updated accordingly.

I don't think code first has this feature yet. It's pretty hard for me to Add data.

I tried using LINQ to check for OpCode and SubOpCode if Name exist. But i don't how to insert data accordingly.

Answer 4

Hi j3r;

The unique constrant is not yet supported by Entity Framework 4.0 - 4.3, You can have a look at this post on Stack Overflow for a possible solution.

Unique Constraint in Entity Framework Code First

 

---

Fernando (MCSD)

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Answer 5

Hi j3r;

One omission from my first solution was that I left out the class constructors. Add the following constructors to the classes.

// For the SubOpCode
public SubOpCode()
{
    OpCodes = new Collection<OpCode>();    
}

// For the OpCode
public OpCode( )
{
    SubOpCodes = new Collection<SubOpCode>( );    
}

To add records to the database you can do the following.

OpCode oc = new OpCode();
oc.CodeName = "Code 1";
SubOpCode soc = new SubOpCode();
soc.CodeName = "code 1";
oc.SubOpCodes.Add(soc);

// ctx is an instance of the DbContext
ctx.OpCodes.Add( oc );
ctx.SaveChanges( );

After doing the above a record will be added to all three tables.

 

---

Fernando (MCSD)

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Answer 6

Thanks for the update. I'm kind of having trouble in the logic part of the code.

I don't know how i can manually update the m-m relationship.

public class OperationDbContext : DbContext
{
    private DbSet<OpCode> OpCodes {get; set; 
    private DbSet<SubOpCode> OpCodes {get; set; 

    public void AddOpcode(Opcode _opCode)
    {
        /*
            if opCode exist
            {
                if subCode don't exist
                {
                    Insert SubOpCode and update m-m relationship
                }
            }
            else opCode don't exist
            {
                Insert OpCode
                
                if subCode don't exist
                {
                    Insert SubOpCode and update m-m relationship
                }
            }
        */

        this.SaveChanges();
    }
}

If it's not possible, probably i will create my m-m and do the LINQ manually. What do you think?

public class OpCode
{
    public int Id { get; set; }
    public String Name { get; set; }
}

public class SubOpCode
{
    public int Id { get; set; }
    public String Name { get; set; }
}

public class OpCodeSubOpCode
{
    public OpCode OpCodeId { get; set; }
    public SubOpCode SubOpCodeId { get; set; }
}

public class OperationDbContext : DbContext
{
    public DbSet<OpCode> { get; set; }
    public DbSet<SubOpCode> { get; set; }
    public DbSet<OpCodeSubOpCode> { get; set; }
}

Answer 7

Hi j3r;

I am not an expert on Windows Form / WPF and the use of IBindingList and seeming this is a different question then the original question of this thread can you post a new question in the correct form for help with this new question.

Thanks;

---

Fernando (MCSD)

If a post answers your question, please click "Mark As Answer" on that post and "Mark as Helpful".

Answer 8

No worries. Many thanks for the help!!