I want to DELETE some items from my Model which I generated from the database like that:
db = new TestDBEntities();
foreach (var item in db.Farbe)
{
_model.Add(new Farbe { FarbauswahlNr = item.FarbauswahlNr, Kurztext = item.Kurztext, Ressource = item.Ressource,Vari1 = Convert.ToBoolean(item.Var1) ,Vari2 = item.Vari2 });
}
I'm showing this Model in a RadGridView and deleting by Selecting and Index per Rightcklick on the mouse like this:
public void ExecuteDelete(object obj)
{
farbliste.Model.Remove(SelectedIndex);
ListeAktualisieren();
}
Now the question is how do I Delete something from my Database because if I just Delete from my Model it wont work and that's also not what I want.
Btw some variable are named in German sorry...
you have to save your context. Your context in the first block of code is db.
So:
db = new TestDBEntities();
db.entity.Remove(db.entity.Find(SelectedIndex));
db.SaveChanges();
Entity is the name of your table/object from entity frramework. I would also suggest wraping this is a using block for the db
Related
I'm currently developing a mobile application who uses a Google App Engine-hosted web service.
But i'm facing an issue. I just want to add a field in one my database's table.
App Engine doesn't use classic SQL syntax, but GQL. So i cannot use the ALTER TABLE statement. How can i do this with GQL ? I looked for a solution on the web, but there's not a lot of help.
public MyEntity() {
}
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
private Key idStation;
private String name;
private double longitude;
private double latitude;
private java.util.Date dateRefresh = new Date(); //the field i want to add in DB
So, now when i create a "MyEntity" object, it should add the "dateRefresh" field into the database... I create my object like this:
MyEntity station = new MyEntity();
station.setName("test");
station.setLatitude(0);
station.setLongitude(0);
station.setDateRefresh(new Date("01/01/1980"));
DaoFactory.getStationDao().addStation(station);
addStation method:
#Override
public MyEntity addStation(MyEntity station) {
EntityManager em = PersistenceManager.getEntityManagerFactory().createEntityManager();
try {
em.getTransaction().begin();
em.persist(station);
em.getTransaction().commit();
} finally {
if(em.getTransaction().isActive()) em.getTransaction().rollback();
em.close();
}
return station;
}
The field "dateRefresh" is never created into my DB...
Someone to help me please ?
Thanks in advance
Just add another field to your data structure, maybe providing a default clause, and that's all. For example, if you have a UserAccount:
class UserAccount(db.Model):
user = db.UserProperty()
user_id = db.StringProperty()
you may easily add:
class UserAccount(db.Model):
user = db.UserProperty()
user_id = db.StringProperty()
extra_info = db.IntegerProperty(default=0)
timezone = db.StringProperty(default="UTC")
and let it go.
While the datastore kinda mimics tables, data is stored on a per entity basis. There is no schema or table.
All you need to do is update your model class, and new entities will be saved with the structure (fields) of the new entity.
Old entities and indexes, however, are not automatically updated. They still have the same fields as they had when they were originally written to the datastore.
There's two ways to do this. One is to make sure your code can handle situations where your new properties are missing, ie make sure no exceptions are thrown, or handle the exceptions properly when you're missing the properties.
The second way is to write a little function (usu a mapreduce function) to update every entity with appropriate or null values for your new properties.
Note that indexes are not updated unless the entity is written. So if you add a new indexed property, old entities won't show up when you query for the new property. In this case, you must use the second method and update all the entities in the datastore so that they are indexed.
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.
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();
}
I have a DataGridView that is bound - via a binding source - to a list of entities:
VehicleRepository:
private IObjectSet<Vehicles> _objectSet;
public VehicleRepository(VPEntities context)
{
_context = context;
_objectSet = context.Vehicles;
}
List<Vehicle> IVehicleRepository.GetVehicles(Model model)
{
return _objectSet
.Where(e => e.ModelId == model.ModelId)
.ToList();
}
In my presenter
private List<Vehicle> _vehicles;
...
_vehicles = _vehicleRepository.GetVehicles(_model);
_screen.BindTo(_vehicles);
in my view
public void BindTo(List<Vehicle> vehicles)
{
_vehicles = vehicles;
if (_vehicles != null)
{
VehicleBindingSource.DataSource = _vehicles;
}
}
This works fine - my grid displays the data as it should. However, in the grid I am wanting to replace the ModelId column with a description field from the Model table. I've tried changing the binding for the column from ModelId to Model.ModelDescription but the column just appears blank.
I'm pretty sure that the data is being loaded, as I can see it when I debug, and when the same list is passed to a details screen I can successfully bind the related data to text fields and see the data.
Am I doing something obviously wrong?
It's a bit manual, but it 'works on my machine'.
Add a column to your DataGridView for the description field and then after you set your DataSource iterate through like so.
Dim row As Integer = 0
foreach (entity In (List<Entity>)MyBindingSource.DataSource)
{
string description = entity.Description;
MyDataGridView.Rows[row].Cells["MyDescriptionCell"].Value = description;
row ++;
}
You get a readonly view of your lookup. I make the new column readonly, but you could write something to handle the user changing the field if you wanted updates to run back to the server. Might be messy though.
The answer involves adding unbound read only columns and setting their value in the DataGridView's DataBindingComplete event
as described here
You can just add a column to your DataGridView, and in the DataPropertyName you must set the [entity].[Field name you need] in your case you could do: VehiclesType.Description
then you must add another binding source for the VehiclesTypes to the form, fill it using your context, and your good to go ;)
My WPF desktop-based application uses ADO.Net Entity Framework in order to connect to SQL Server database. In one of the windows I have a DataGrid with all data from tbl_users, when user selects one of the rows (records) and clicks on Edit, application opens a new window with form, that includes all data that user can edit/update.
How to save changes (update/edit) of one of the table's values to database via ADO.NET Entity Framework?
Here are some code snippets that help understand a situation:
1 - Edit window constructor
public object objToBeEdited;
public WinWorkers_EditWorker(tbl_users userToBeEdited){
this.Title = Glidus.Properties.Resources.WinWorkers_EditWorker_WinName + Glidus.Properties.Resources.WinApp_WinName;
}
2 - Method Update, that doesn't work
//assume inputted values to new object
tbl_users newUser = new tbl_users() {
userName = this.WinWorkers_AddEditWorkers_Form_UserName.Text,
userPassword = this.WinWorkers_AddEditWorkers_Form_Password.Text,
userAccessLevel = this.WinWorkers_AddEditWorkers_Form_UserAccessLevel.Text
};
//default minimal password length is 4
if (App.IsInputValueMinLenOK(newUser.userPassword, 4)) {
EntityKey key = App.glidusContext.CreateEntityKey("tbl_users", objToBeEdited);
if (App.glidusContext.TryGetObjectByKey(key, out objToBeEdited)) {
App.glidusContext.ApplyCurrentValues<tbl_users>(key.EntitySetName, newUser);
}
try {
App.glidusContext.SaveChanges();
}
catch (Exception ex) {
App.UnitedHandleException(ex);
}
}
Please, help me, how to implement update ADO.NET record from the database. For example, in my table there is James Bond 007, after editing page (clicking in submit page) I see Austin Powers 008.
To edit or update you can use stub entities
Category category = new Category { ID = 5};
Context.AttachTo(“Categories”,category);
Product product = new Product {
Name = “Bovril”,
Category = category
};
Context.AddToProducts(product);
Context.SaveChanges();
I have a grid bound to a BindingSource which is bound to DataContext table, like this:
myBindingSource.DataSource = myDataContext.MyTable;
myGrid.DataSource = myBindingSource;
I couldn't refresh BindingSource after insert. This didn't work:
myDataContext.Refresh(RefreshMode.OverwriteCurrentValues, myBindingSource);
myBindingSource.ResetBinding(false);
Neither this:
myDataContext.Refresh(RefreshMode.OverwriteCurrentValues, myDataContext.MyTable);
myBindingSource.ResetBinding(false);
What should I do?
I have solved the problem but not in a way I wanted.
Turns out that DataContext and Linq To SQL is best for unit-of-work operations. Means you create a DataContext, get your job done, discard it. If you need another operation, create another one.
For this problem only thing I had to do was recreate my DataContext like this.dx = new MyDataContext();. If you don't do this you always get stale/cached data. From what I've read from various blog/forum posts that DataContext is lightweight and doing this A-OK. This was the only way I've found after searching for a day.
And finally one more working solution.
This solution works fine and do not require recreating DataContext.
You need to reset internal Table cache.
for this you need change private property cachedList of Table using reflection.
You can use following utility code:
public static class LinqDataTableExtension
{
public static void ResetTableCache(this ITable table)
{
table.InternalSetNonPublicFieldValue("cachedList", null);
}
public static void ResetTableCache(this IListSource source)
{
source.InternalSetNonPublicFieldValue("cachedList", null);
}
public static void InternalSetNonPublicFieldValue(this object entity, string propertyName, object value)
{
if (entity == null)
throw new ArgumentNullException("entity");
if(string.IsNullOrEmpty(propertyName))
throw new ArgumentNullException("propertyName");
var type = entity.GetType();
var prop = type.GetField(propertyName, BindingFlags.NonPublic | BindingFlags.Instance);
if (prop != null)
prop.SetValue(entity, value);
// add any exception code here if property was not found :)
}
}
using something like:
var dSource = Db.GetTable(...)
dSource.ResetTableCache();
You need to reset your BindingSource using something like:
_BindingSource.DataSource = new List();
_BindingSource.DataSource = dSource;
// hack - refresh binding list
Enjoy :)
Grid Data Source Referesh by new query instead just Contest.Table.
Simple Solution < But Working.
Whre is eg.
!!!!! Thanks - Problem Solved after no of days !!! but with so simple way ..
CrmDemoContext.CrmDemoDataContext Context = new CrmDemoContext.CrmDemoDataContext();
var query = from it in Context.Companies select it;
// initial connection
dataGridView1.DataSource = query;
after changes or add in data
Context.SubmitChanges();
//call here again
dataGridView1.DataSource = query;
I have the same problem. I was using a form to create rows in my table without saving the context each time. Luckily I had multiple forms doing this and one updated the grid properly and one didn't.
The only difference?
I bound one to the entity similarly (not using the bindingSource) to what you did:
myGrid.DataSource = myDataContext.MyTable;
The second I bound:
myGrid.DataSource = myDataContext.MyTable.ToList();
The second way worked.
I think you should also refresh/update datagrid. You need to force redraw of grid.
Not sure how you insert rows. I had same problem when used DataContext.InsertOnSubmit(row), but when I just inserted rows into BindingSource instead BindingSource.Insert(Bindingsource.Count, row)
and used DataContext only to DataContext.SubmitChanges() and DataContext.GetChangeSet(). BindingSource inserts rows into both grid and context.
the answer from Atomosk helped me to solve a similar problem -
thanks a lot Atomosk!
I updated my database by the following two lines of code, but the DataGridView did not show the changes (it did not add a new row):
this.dataContext.MyTable.InsertOnSubmit(newDataset);
this.dataContext.SubmitChanges();
Where this.dataContext.MyTable was set to the DataSource property of a BindingSource object, which was set to the DataSource property of a DataGridView object.
In code it does looks like this:
DataGridView dgv = new DataGridView();
BindingSource bs = new BindingSource();
bs.DataSource = this.dataContext.MyTable; // Table<T> object type
dgv.DataSource = bs;
Setting bs.DataSource equals null and after that back to this.dataContext.MyTable did not help to update the DataGridView either.
The only way to update the DataGridView with the new entry was a complete different approach by adding it to the BindingSource instead of the corresponding table of the DataContext, as Atomosk mentioned.
this.bs.Add(newDataset);
this.dataContext.SubmitChanges();
Without doing so bs.Count; returned a smaller number as this.dataContext.MyTable.Count();
This does not make sense and seems to be a bug in the binding model in my opinion.