When i am trying to clear my observable collection it is crashing.Is there any
other way to clear it??
ObservableCollection<Group> _groupList = new ObservableCollection<Group>();
public ObservableCollection<Group> GroupList
{
get
{
return _groupList;
}
set
{
_groupList = value;
RaisePropertyChanged("GroupList");
}
}
You can simple make a new collection:
GroupList = new ObservableCollection<Group>();
There's a clear function
GroupList.Clear();
or
GroupList = new ObservableCollection<Group>();
Also try declare you list this way :
ObservableCollection<Group> _groupList;
public ObservableCollection<Group> GroupList
{
get { return _groupList; }
set { SetValue(ref _groupList, value); }
}
Related
Usually CollectionModel will return an _embedded array, but in this example:
#GetMapping("/{id}/productMaterials")
public ResponseEntity<?> getProductMaterials(#PathVariable Integer id) {
Optional<Material> optionalMaterial = materialRepository.findById(id);
if (optionalMaterial.isPresent()) {
List<ProductMaterial> productMaterials = optionalMaterial.get().getProductMaterials();
CollectionModel<ProductMaterialModel> productMaterialModels =
new ProductMaterialModelAssembler(ProductMaterialController.class, ProductMaterialModel.class).
toCollectionModel(productMaterials);
return ResponseEntity.ok().body(productMaterialModels);
}
return ResponseEntity.badRequest().body("no such material");
}
if the productMaterials is empty CollectionModel will not render the _embedded array which will break the client. Is there any ways to fix this?
if (optionalMaterial.isPresent()) {
List<ProductMaterial> productMaterials = optionalMaterial.get().getProductMaterials();
CollectionModel<ProductMaterialModel> productMaterialModels =
new ProductMaterialModelAssembler(ProductMaterialController.class, ProductMaterialModel.class).
toCollectionModel(productMaterials);
if(productMaterialModels.isEmpty()) {
EmbeddedWrappers wrappers = new EmbeddedWrappers(false);
EmbeddedWrapper wrapper = wrappers.emptyCollectionOf(ProductMaterialModel.class);
Resources<Object> resources = new Resources<>(Arrays.asList(wrapper));
return ResponseEntity.ok(new Resources<>(resources));
} else {
return ResponseEntity.ok().body(productMaterialModels);
}
}
How may I avoid to duplicate the code I use for mapping a database entity to a poco object?
Given this code:
private IQueryable<DummyExtended> Find()
{
return (from dt in Entities.dummy_table
select new DummyExtended
{
Description = dt.table_1.table_2.description,
Dummy = new Dummy
{
Name = d.name,
Notes = d.notes,
HelpText = d.help_text
}
}).AsQueryable();
}
Can I create a common linq expression to be re-used for both methods?
private IQueryable<DummyExtended> Find()
{
return (from dt in Entities.dummy_table
select new DummyExtended
{
Description = dt.table_1.table_2.description,
Dummy = ...???
}).AsQueryable();
}
private IQueryable<DummyAlsoExtended> FindAnother()
{
return (from dt in Entities.dummy_table
select new DummyAlsoExtended
{
InnerHtml = dt.table_html.description,
Dummy = ....??
}).AsQueryable();
}
Example:
public static Expression<Func<dummy_table, Dummy>> EntityToPoco()
{
return d => new Dummy
{
Name = d.name,
Notes = d.notes,
HelpText = d.help_text
};
}
I can't quite get it right
....
Dummy = ExtensionClass.EntityToPoco()
So you have a dummy_table which is a Enumerable or Queryable sequence of objects. Let's assume that the sequence contains objects of class DummyTableElement.
You showed, that if you have a DummyTableElement you know how to convert it into a Dummy object. You want to reuse this function to create other objects like DummyExtended and DummyAlsoExtended. If you want to do this LINQ-alike, it is best to create extension functions for it:
static class DummyTableElementExtensions
{
public static Dummy ToDummy(this TableElement tableElement)
{
return new Dummy()
{
Name = tableElement.name,
Notes = tableElement.notes,
HelpText = tableElement.help_text
};
}
}
Once you have this, you can create similar functions to convert TableElements into DummyExtended and DummyAlsoExtended. They will be one-liners.
In the same extension class:
public static DummyExtended ToDummyExtended(this TableElement tableElement)
{
return new DummyExtended()
{
Description = tableElement.table_1.table_2.description,
Dummy = tableElement.ToDummy(),
};
}
public static DummyAlsoExtended ToDummyAlsoExtended(this TableElement tableElement)
{
return new DummyAlsoExtended
{
InnerHtml = tableElement.table_html.description,
Dummy = tableElement.ToDummy(),
};
}
And once you've got these, you can create extension functions to convert any IQueryable of TableElements:
public static IQueryable<DummyExtended> ToDummyExtended(
this IQueryable<TableElement> tableElements)
{
return tableElements
.Select(tableElement => tableelement.ToDummyExtended();
}
And a similar one-line function for DummyAlsoExtended.
Your Find function and FindAnother function will also be one-liners:
private IQueryable<DummyExtended> Find()
{
return dummy_table.ToDummyExtended();
}
private IQueryable<DummyAlsoExtended> FindAnother()
{
return dummy_table.ToDummyAlsoExtended();
}
I'm not sure why you wanted to use an expression in this. It doesn't seem that DummyExtended and DummyAlsoExtended are really similar, except that they both have a property Dummy.
One reason to parameterize the destination of your find function could be because you want to create anonymous classes in your Find function.
Again, once you've created ToDummy this will be a one-liner:
public static IQueryable<TResult> Find<TSource, TResult>(
this IQueryable<TSource> source,
Expression<Func<TSource, TResult>> resultSelector)
{
return source.Select(sourceElement => resultSelector(sourceElement);
}
Usage would be:
var X = dummy_Table.find(tableElement => new
{
foo = tableElement.CalculateFoo(),
bar = tableElement.CalculateBar(),
Dummy = tableElement.ToDummy(),
});
I have a Shared Project where I have changed the database to Realm instead of SQLite.
My problem is, if I close the Realm in my DatabaseManager, the result is removed. Therefore i have created a static singelton instance of the Realm, which all my DatabaseManager use. Now my app crash after short time on memory, and if i remove all my database-functions, it works.
I create my Realm-instance here:
public class RealmDatabase
{
private Realm mRealmDB;
public Realm RealmDB
{
get
{
if (mRealmDB == null || mRealmDB.IsClosed)
{
SetRealm ();
}
return mRealmDB;
}
}
static RealmDatabase cCurrentInstance;
public static RealmDatabase Current
{
get
{
if (cCurrentInstance == null)
cCurrentInstance = new RealmDatabase ();
return cCurrentInstance;
}
}
public RealmDatabase ()
{
}
private void SetRealm ()
{
var config = new RealmConfiguration ("DBName.realm", true);
mRealmDB = Realm.GetInstance (config);
}
public Transaction BeginTransaction ()
{
return RealmDB.BeginWrite ();
}
}
The I have my DatabaseManagler looking like this:
public class NewFreeUserManager
{
internal Realm RealmDB = RealmDatabase.Current.RealmDB;
static NewFreeUserManager cCurrentInstance;
public static NewFreeUserManager Current
{
get
{
if (cCurrentInstance == null)
cCurrentInstance = new NewFreeUserManager ();
return cCurrentInstance;
}
}
private NewFreeUserManager ()
{
}
internal bool Save (FreeUser freeuser)
{
try
{
using (var trans = RealmDB.BeginWrite ())
{
RealmDB.RemoveAll<FreeUser> ();
var fu = RealmDB.CreateObject<FreeUser> ();
fu = freeuser;
trans.Commit ();
}
return true;
}
catch (Exception e)
{
Console.WriteLine ("FreeUser save: " + e.ToString ());
return false;
}
}
internal FreeUser Get ()
{
return RealmDB.All<FreeUser> ().FirstOrDefault ();
}
}
Can anyone help me?
there are a few issues with your current setup that prevent you from persisting objects properly.
The first and very important one is that Realm instances are not thread-safe. That is, using them as singletons is strongly discouraged, unless you are certain that you'll never access them from another thread.
The second is more subtle, but in your save method you are calling:
var fu = RealmDB.CreateObject<FreeUser>();
fu = freeuser;
What it does is, effectively, you are creating an object in the Realm, and then assigning the variable to another object. This will not assign freeuser's properties to fu, it just replaces one reference with another. What you're looking for is Realm.Manage so your code should look like this:
using (var trans = RealmDB.BeginWrite())
{
RealmDB.Manage(freeuser);
trans.Commit();
}
Once you fix the second bug, you should be able to go back and close Realm instances when you don't need them anymore.
I will call AnalyseLinqUpdate()
I think code itself clear..
I have to find behavior for each dictionary value and replace the value with the behavior I get from the method 'GiveBehavior'
void AnalyseLinqUpdate()
{
Dictionary<string, string> rawCollection = new Dictionary<string, string>();
rawCollection.Add("PT-1", "PTC-1");
rawCollection.Add("PT-2", "PTC-1");
rawCollection.Add("PT-3", "PTC-2");
rawCollection.Add("PT-4", "PTC-2");
rawCollection.Add("PT-5", "PTC-3");
rawCollection.Add("PT-6", "PTC-3");
//update here
// call GiveBehavior("PTC-1");
//returns a string that needs to be updated in place of "PTC-1"
}
string GiveBehavior(string ptc)
{
StringComparison ignoreCase = StringComparison.OrdinalIgnoreCase;
ptc = ptc.Trim();
if (ptc.Equals("PTC-1", ignoreCase))
{
return "PTB-1";
}
else if (ptc.Equals("PTC-1", ignoreCase))
{
return "PTB-2";
}
else
{
return "PTB-3";
}
}
Currently I have done like:
List<string> keys = rawCollection.Keys.ToList();
foreach (string key in keys)
{
string behavior = GiveBehavior(rawCollection[key]);
rawCollection[key] = behavior;
}
This is how I update the dictionary..
Is there anyway tat can be done via LINQ...
You could try the following:
List<string> keys = rawCollection.Keys.ToList();
keys.ForEach(key => { rawCollection[key] = GiveBehavior(rawCollection[key]); });
That should do it
rawCollection = rawCollection.ToDictionary(item => item.Key, item => GiveBehavior(item.Key));
Assume that we have class
public class RMenuItem
{
public List<RMenuItem> ChildrenItems { get; }
public decimal OperationID { get; }
public string Name { get; }
}
as you can see - each menuitem could have children items - as usual in menu.
My task is to iterate through each items of this list and apply some action to it. Classical decision is to write recursive iteration. But I'm interesting if LINQ could make my task easier? For example, I suppose that we can write query that can get flat list of objects, which i can iterate simply with foreach. But my attempts in this way weren't successful yet.
So any help appreciated!
It's possible:
public void PrintAllNames(RMenuItem rootItem)
{
Action<RMenuItem> print = null;
print = m =>
{
Console.WriteLine(m.Name);
m.ChildrenItems.ForEach(print);
};
print(rootItem);
}
Notice how it's necessary to declare print so that print can use itself. This is directly comparable to a recursive method, which I'd rather use:
public void PrintAllNames(RMenuItem rootItem)
{
Console.WriteLine(rootItem.Name);
rootItem.ChildrenItems.ForEach(PrintAllNames);
}
(although for a more complex situation, maybe the functional solution would make the most sense)
I suggest 2 ways of achieving this. You can opt with an utility method to get all the items or you can implement the Visitor Pattern, though it implies changing the RMenuItem class.
Utility method:
static IEnumerable<RMenuItem> GetAllMenuItems(IList<RMenuItem> items)
{
if (items == null)
throw new ArgumentNullException("items");
Queue<RMenuItem> queue = new Queue<RMenuItem>(items);
while (queue.Count > 0)
{
var item = queue.Dequeue();
if (item.ChildrenItems != null)
{
foreach (var child in item.ChildrenItems)
{
queue.Enqueue(child);
}
}
yield return item;
}
}
I prefer an imperative way to a recursive because we can use iterator blocks.
Visitor Pattern:
public interface IRMenuItemVisitor
{
void Visit(RMenuItem item);
}
public class PrintRMenuItemVisitor : IRMenuItemVisitor
{
public void Visit(RMenuItem item)
{
Console.WriteLine(item);
}
}
public interface IRMenuItem
{
void Accept(IRMenuItemVisitor visitor);
}
public class RMenuItem : IRMenuItem
{
// ...
public void Accept(IRMenuItemVisitor visitor)
{
visitor.Visit(this);
if (ChildrenItems != null)
{
foreach (var item in ChildrenItems)
{
item.Accept(visitor);
}
}
}
}
Usage:
RMenuItem m1 = new RMenuItem
{
Name = "M1",
ChildrenItems = new List<RMenuItem> {
new RMenuItem { Name = "M11" },
new RMenuItem {
Name = "M12",
ChildrenItems = new List<RMenuItem> {
new RMenuItem { Name = "M121" },
new RMenuItem { Name = "M122" }
}
}
}
};
RMenuItem m2 = new RMenuItem
{
Name = "M2",
ChildrenItems = new List<RMenuItem> {
new RMenuItem { Name = "M21" },
new RMenuItem { Name = "M22" },
new RMenuItem { Name = "M23" }
}
};
IList<RMenuItem> menus = new List<RMenuItem> { m1, m2 };
foreach (var menu in GetAllMenuItems(menus))
{
Console.WriteLine(menu);
}
// or
IList<RMenuItem> menus = new List<RMenuItem> { m1, m2 };
foreach (var menu in menus)
{
menu.Accept(new PrintRMenuItemVisitor());
}
You could difine a Flatten method in your class (or as an extension if you prefer) like this
public IEnumerable<RMenuItem> Flatten()
{
foreach (var item in ChildrenItems)
{
yield return item;
}
return ChildrenItems.SelectMany(item => item.Flatten());
}
then doing somthing with each elements will be as simple as
RMenuItem rootItem ;
// do somthing with the root item
foreach (var item in rootItem.Flatten())
{
// do somthing
}
Indeed you can do that using LINQ, SelectMany flats out the list, just some example
menuItemsList.SelectMany(x => x.ChildrenItems).Where(c => c.someChildProperty);
Thanks
Edit:
In response to the comments, I was just giving an example of SelectMany previously. Thanks for pointing out.
menuItemsList.SelectMany(x => x.ChildrenItems.Select(p => p)).Where(c => c.someChildProperty);
OR something like this
menuItemsList.SelectMany(x => x.ChildrenItems).Select(p => p).Where(c => c.someChildProperty);
Edit2
Ahh .. now I understood what you want ..
We can just slightly modify my above query to do what you want
menuItemsList
.SelectMany(x => { //do something with x like printing it
x.ChildrenItems
})
.Select(p => { // do something with p like printing it
p
});
Basically you can do what you want the element inside the {}
Thanks