how to update dataset from obseravable collections as values updated in Obseravable collections

i am currently working on POS & Inventory Application , i am loading the products and stocks available data from the databse to dataset then dataset to obseravable collection . finally obseravable collection is binded to UI Controls like Data grid and List view.

Now , i want to update the changes made in observable collection by the user using UI Controls to data set and then to database file (SDF) ... please , show the possible coding to update the dataset from observable collection as observable collection changes

One of our friend in this forum gave a example to convert dataset to obseravable collection . i tried that and worked well .

code goes like this 1. Person class to hold My Person dat开发者_如何学JAVAa:

public class Person
{
public int Id { get; set; }
public string Name { get; set; }
public int Age { get; set; }
}

Then used LINQ to populate My ObservableCollection:

var people = new ObservableCollection<Person>(
dataset.Tables["Person"].AsEnumerable().Select(p => new Person
{
    Id = p.Field<int>("Id"),
    Name = p.Field<string>("Name"),
    Age = p.Field<int>("Age")
}));

its working well, now, moving further i want to update back dataset from obseravable collection as ObseravableCollection changes in UI Datagrid entries changes

please explain me about possible coding to achieve this task.

I see two options

first you can subscribe to PropertyChanged event of every object in ObservableCollection, and to CollectionChanged event of ObservableCollection to keep this 2 data structures in synch

and second, which is more easy to implement I think, is to create property with unchanged,added, modified,deleted enum vales in your class, set this property depending user actions, and convert this to DataSet when saving

EDIT

Here is a simple implementation for second method

create enum like this

public enum DataObjectState
{
  Unchanged,
  Added,
  Modified,
  Deleted
}

Than add property to your class like this

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
    public DataObjectState ObjectState{get;set;}
}

after which you can create ObservableCollection form dataset like you show

dataset.Tables["Person"].AsEnumerable().Select(p => new Person
{
    Id = p.Field<int>("Id"),
    Name = p.Field<string>("Name"),
    Age = p.Field<int>("Age"),
    ObjectState = ConvertRowStateToObjectState(p.RowState)
}));

and can convert from observablecollection to dataset by using opposite query

EDIT

private DataObjectState ConvertRowStateToObjectState(DataRowState dataRowState)
        {
            return (DataObjectState)Enum.Parse(typeof(DataObjectState), dataRowState.ToString());
        }

I doesn't find a way to create dataset with Linq too, but here is a bit hack method to do what you want

        DataTable personsTable = new DataTable("Person");
        personsTable.Columns.Add("Id", typeof(int));
        personsTable.Columns.Add("Name", typeof(string));
        personsTable.Columns.Add("Age", typeof(int));

        foreach (var item in collection)
        {
            DataRow row = personsTable.NewRow();
            row["Id"] = item.Id;
            row["Name"] = item.Name;
            row["Age"] = item.Age;
            personsTable.Rows.Add(row);
            if (item.ObjectState == DataObjectState.Added)
            {
                continue;
            }
            row.AcceptChanges();
            if (item.ObjectState == DataObjectState.Deleted)
            {                   
                row.Delete();
            }
            else if (item.ObjectState == DataObjectState.Modified)
            {
                row.BeginEdit();
                row.EndEdit();
            }
        }

Beside @ArsenMkrt-s solution you can also think of using a strong typed dataset that will have a PersonTable-class instead of the observable Collection and a PersonRow-class instead of your current Person-Class.

These can be bound to a datagrid, too.

The benefit: no conversion-code required.

you can use a filtered collectionviewsource for 2 good thinks : 1-it's not a new collection (less memory need). 2-it's like collection of pointers upon your Table with 2 ways databinding capability.