linq reflection WInForms - winforms

Question

I am very new to linq and am trying to figure out how to accomplish the following:
Currently, I have a Winforms project that has a Base Form with a DataRow as one of it's members. I have several derived Forms populate the DataRow based on data from a DataTable (SQL Query Result). There are controls on the derived Forms that are populated with the values from the data as well. When the Save button on the derived Forms is clicked, the DataRow in the Base Form is updated and then the Derived Form updates the Database via a DataAdapter.
I wanted to replace all of the SQL Commands using linqs so I tried implementing this functionality using LINQ by the following:
I created my Linq query in the Derived Form and assigned the result to an Object in the Base Form. I cast the Object in the Base Form to the class type of the Linq query and use reflection to populate all the controls on the Derived Form. When the save button is clicked I update the Object but I am not able to update the Database.
The problem that I can't solve is how to update the database once the object is updated. At this point I don't have the Data Context that I used for the linq query.
I am using an SQL function within the linq query so I had to create a separate class for these values as I was getting an anonymous type error. I am probably missing something here.
Any help would be most appreciated as I really how clean the linq code is.
Edit (Copied from Brad's Edit to Tomas's answer):
Here are the 3 steps of my code.
Step 1 - Get a singe record of data from database
private void GetDatabaseDetailData()
{
_db = new PriorityDataContext();
DetailData = (from db in _db.tblDatabases
where db.DatabaseID == Id
select db).SingleOrDefault();
DeveloperData = (from db in _db.tblDatabases
where db.DatabaseID == Id
select new DeveloperInfo
{
DeveloperName = _db.func_get_employee_name(db.Developer)
}).SingleOrDefault();
}
Step 2 - Populate all controls whos name exists in the Object. The DetailData Object is cast to the specific type passed into this method. All code not shown for brevity.
protected virtual void PopulateDetailControlsA(List<Control> controlContainers, string srcDataTableName)
{
Object data = null;
Type type = null;
switch (srcDataTableName)
{
case "tblDatabases" :
type = typeof(tblDatabase);
data = (tblDatabase)DetailData;
break;
}
if (type != null)
{
var properties = type.GetProperties(BindingFlags.Public | BindingFlags.Instance);
foreach (var controlContainer in controlContainers)
{
foreach (var propertyInfo in properties)
{
if (!ControlExists(controlContainer, propertyInfo.Name)) continue;
var txtControl = controlContainer.Controls[propertyInfo.Name] as ExtendedTextBox;
if (txtControl != null)
{
try
{
var value = propertyInfo.GetValue(data, null).ToString();
if (propertyInfo.Name == "row_oper_name" || propertyInfo.Name == "row_last_chng_oper_name")
{
txtControl.Text = RowOperatorData.RowOperatorName;
txtControl.ValueMember = propertyInfo.GetValue(data, null).ToString();
}
else
txtControl.Text = value;
}
catch (NullReferenceException)
{
}
continue;...........
Step 3 - Try and save changes back to database in the derived From.
private void SaveData()
{
try
{
_db.SubmitChanges();
}
catch (Exception sqlException)
{
}
}
What I am really unclear about hear is how to store the result set in the Base Form so that I can use the same code for many different queries. The DataRow worked great because I use the some code for over 25 derive Forms.

Answer 1

If I understand you correctly, you create the DataContext in a derived form and then use it to write some queries (in a derived form). In order to be able to update the database, your queries must return the entities obtained from the table (i.e. the select clause should just return the entity). For example:
DataContext db = // ...
var q = from p in db.Things
where p.Some > 10 select p;
If you then modify the entities, you can use db.SubmitChanges() to store the changes (made to the entity objects) to the database. For this, you need the original db value.
In your scenario, you'll need to store the DataContext (as a field) in the derived form. If you need to perform the update from the base form, then I suggest you define a virtual method:
// Base form
protected abstract void UpdateDatabase();
// Derived from with field 'db' storing 'DataContext'
protected override void UpdateDatabase() {
db.SumbitChanges();
}