How to change the value of associated field

Question

I have 2 classes with a LINQ association between them i.e.:

Table1:       Table2:
ID            ID
Name          Description
              ForiegnID
<         


        

Answer 1

You wanna to associate with another record in table1 or change table1.id? if it's option 1, you need to remove that association and set a new one. If option 2, check you db and see if update cascade yes enabled for this fk and than get record and change value of id.

Answer 2

Check out the designer.cs file. This is the key's property

[Column(Storage="_ParentKey", DbType="Int")]
public System.Nullable<int> ParentKey
{
    get
    {
        return this._ParentKey;
    }
    set
    {
        if ((this._ParentKey != value))
        {
            //This code is added by the association
            if (this._Parent.HasLoadedOrAssignedValue)
            {
                throw new System.Data.Linq.ForeignKeyReferenceAlreadyHasValueException();
            }
            //This code is present regardless of association
            this.OnParentKeyChanging(value);
            this.SendPropertyChanging();
            this._ParentKey = value;
            this.SendPropertyChanged("ParentKey");
            this.OnServiceAddrIDChanged();
        }
    }
}

And this is the associations property.

[Association(Name="Parent_Child", Storage="_Parent", ThisKey="ParentKey", IsForeignKey=true, DeleteRule="CASCADE")]
public Parent Parent
{
    get
    {
        return this._Parent.Entity;
    }
    set
    {
        Parent previousValue = this._Parent.Entity;
        if (((previousValue != value) 
                    || (this._Parent.HasLoadedOrAssignedValue == false)))
        {
            this.SendPropertyChanging();
            if ((previousValue != null))
            {
                this._Parent.Entity = null;
                previousValue.Exemptions.Remove(this);
            }
            this._Parent.Entity = value;
            if ((value != null))
            {
                value.Exemptions.Add(this);
                this._ParentKey = value.ParentKey;
            }
            else
            {
                this._ParentKey = default(Nullable<int>);
            }
            this.SendPropertyChanged("Parent");
        }
    }
}

It's best to assign changes through the association instead of the key. That way, you don't have to worry about whether the parent is loaded.

Answer 3

Table1:       Table2:
ID            ID
Name          Description
              ForeignID

With this :

Table2.ForeignID = 2

you receive an error..........

Example :

You can change ForeignID field in Table 2 whit this :

   Table2 table = dataContext.Table2.single(d => d.ID == Id)

   table.Table1 = dataContext.Table1.single(d => d.ID == newId);

Where the variable newId is the id of the record in Table 2 that would you like associate whit the record in Table 1