I am getting a strange issue with xamarin essentials preferences documentation I am getting a time out the issue at present.
var warehouseFromId = Preferences.Get("WarehouseFromId", "");
WarehouseFromId = Convert.ToInt64(warehouseFromId);
I am setting the value as such using a constructor method called savedSettings but sometimes that won't be called till the user has clicked a button, so why is my getting a cast exception.
public string WarehouseFromName { get; set; }
public long WarehouseFromId { get; set; }
warehouseFromName="TT";
WarehouseFromId=1839;
Preferences.Set("WarehouseFrom", warehouseFromName);
Preferences.Set("WarehouseFromId", WarehouseFromId);
So I thought may have been because I am using "" which would denote a string so i tried the following.
var warehouseFromId = Preferences.Get("WarehouseFromId", 0);
I got the bellow
Unhandled Exception:
Java.Lang.ClassCastException: then i got this after my test above
Unhandled Exception:
System.MissingMethodException: Method not found: int
Xamarin.Essentials.Preferences.Get(string,int)
According to your code, you could need to take a care Convert.ToInt64(), Converts a specified value to a 64-bit signed integer, it is not a empty or null.
Preferences.Get() is to retrieve a value from preferences or a default if not set, so If you want to use Preferences.Get() to set vakue firstly, then retrive this value, please confirm you don't use Preferences.Set("my_key", "my_value") to set value before, otherwise it will report a error.
public string WarehouseFromName { get; set; }
public long WarehouseFromId { get; set; }
public long Id { get; set; }
Preferences.Clear();
WarehouseFromName = "TT";
WarehouseFromId = 1839;
Preferences.Set("WarehouseFrom", WarehouseFromName);
Preferences.Set("WarehouseFromId", WarehouseFromId);
Console.WriteLine("the WarehouseFromId is {0}",Convert.ToInt64(WarehouseFromId));
Id= Preferences.Get("Id", 0);
Console.WriteLine("the value is {0}",Convert.ToInt64(Id));
Related
I have the following code:
var aaData = myapi.GetData().AsEnumerable().Select(x => new {
Id = x["myID"],
Desc = x["myDesc"]
});
Trying to do the following
aaData = aaData.OrderBy((string.Join(",", request.Order
.Select(x => request.Columns[x.Column].Data + " " + x.Dir))));
Getting error:
CS0266 Cannot implicitly convert type 'System.Collections.Generic.IEnumerable<>' to 'System.Data.EnumerableRowCollection<>'. An explicit conversion exists (are you missing a cast?)
How to fix this?
GetData returns a DataTable
Request is an object having a property:
public OrderCol[] Order { get; set; }
OrderCol is
public class OrderCol {
public int Column { get; set; }
public string Dir { get; set; }
}
Thanks for your assistance.
The above code works for the case when I get a List<> back instead of DataTable. The error states that a Cast is needed and it seems to be how DataTable.AsEnumerable is set up as a EnumerableRowCollection
Can use a mock datatable to mimic the above
DataTable dt = new DataTable();
dt.clear();
dt.Columns.Add("myID");
dt.Columns.Add("myDesc");
all i needed was to convert to a list and things worked fine
Can anyone tell me if they have run into any "memory" limitations with Xamarin Forms App for Android?
I recently decided to give Xamarin another go... A few years back I ran into far too many hurdles and went a different route. I hoped things had changed.
I have an empty Xamarin Forms App for Android ONLY at this point (no OSX or UWP support). I created and updated the initial app (4.3 Xamarin Forms). I modified the mainpage.xaml and the mainpage.xaml.cs. Simple 3 row grid... 2 columns... first row, small header image centered columnspan="2"... Second row is also centered, with a CollectionView to "horizontally" scroll some simple small icon/images... Third row of gird is for detail (not yet implemented). So, with this, you can see the application is still quite small and has no real magic going on... Here is the delimma...
I have 8 c# Objects that are a c# Class... I began building the application using a simplified version of the class... Name, and ImageName only for the purpose of testing the 4.3 CollectionView for a navigation UI... After I had the functionality I wanted and it was running and tested for deployment to device, Everything seemed fine... So, I continued and built out the full class objects (13 fields, all strings no real data entered, just empty quotes for value = "". The only fields I have filled in are the original Name and ImageName is code read only... Running the App in the emulator, it now fails on load... and the emulator asks if I would like to close or try and reload...
It seems that my display class, when the class has more than the first few fields filled in causes some sort of overload:
var displaylist = new List<"DisplayClass"> ();
var dc = New DisplayClass({Name = "This Icon"})... add all 8 and things are working...
var dc = new DisplayClass({Name="This Icon", State="MA", Style="", Definition="", ... all others empty string});
--- add all 8 classes with names only and all empty fields... fails to load app...
public class DisplayClass
{
public string Name { get; set; }
public string State { get; set; }
public string Style { get; set; }
public string Definition { get; set; }
public string Days { get; set; }
public string Time { get; set; }
public DateTime StartDate { get; set; }
public string Imageurl { get; set; }
public string Dataurl { get; set; }
public string Retrievalurl { get; set; }
public string LastRetrievalDate { get; set; }
public string LastInfoData { get; set; }
public string Quantity { get; set; }
public string ImageName
{
get { return Name.Replace(" ", string.Empty).ToLower(); }
}
}
I updated the emulator to use 4GB instead of 1GB, but that had no effect. There are no code errors that I can tell, if I remark out the full object classes and implement the stripped out version it works without error... I do not get an error, only a App failed to start dialog from Android...
Can anyone shed light on this?
My bad... I had an un-instantiated datetime in my class... oops... sorry folks!
I have a ViewModel with a String property and the following Data Annotation :
Edit to work with string
[DataType(DataType.Date, ErrorMessage="Not Working !!!")]
public String StringBirthDate1 { get; set; }
That's my view
#Html.EditorFor(model => model.StringBirthDate1 )
#Html.ValidationMessageFor(model => model.StringBirthDate1)
If I run my application and put an invalid Date like '---' or 29.02.1900 I don't get any validation error !
Ok I've given up trying to use built-in MVC tools for data validation !
I did a custom Validation Attribute :
public class ValidDateStringAttribute : ValidationAttribute
{
public override bool IsValid(object value)
{
DateTime dtout;
if (DateTime.TryParse(value.ToString(), out dtout ))
{
return true;
}
return false;
}
}
Here is my View Model decorated with the custom attribute :
[ValidDateString(ErrorMessage="Invalid date format")]
public String BirthDate1 { get; set; }
Works like a charm :-)
It seems to me, that [DataType(DataType.Date, ErrorMessage="Not Working !!!")] working when it attached to string property. Try to use:
[DataType(DataType.Date, ErrorMessage="Not Working !!!")]
puplic string StringBirthDate1{get;set;}
public DateTime BirthDate1
{
get{return DateTime.Parse(StringBirthDate1);}
set{StringBirthDate1 = value.ToString();}
}
I didn't like any of the solutions I found so I kept poking at possibilities until I came up with one I do like. I added a regular expression validator utilizing the regular expression from this article: http://answers.oreilly.com/topic/226-how-to-validate-traditional-date-formats-with-regular-expressions/
[Required(ErrorMessage = "Birthdate is required. [MM/DD/YYYY]")]
[RegularExpression(#"^([1-9]|0[1-9]|1[0-2])[- / .]([1-9]|0[1-9]|1[0-9]|2[0-9]|3[0-1])[- / .](1[9][0-9][0-9]|2[0][0-9][0-9])$", ErrorMessage = "Birthdate must be in MM/DD/YYYY format.")]
public Nullable<DateTime> Birthdate { get; set; }
The result is, if the field is blank I get the required error message and if anything is in the field, but it is not a valid date, I get the regular expression message.
I might add that it seems very silly that [DataType] doesn't accept an error message. I tried exactly like the original author of this thread. That would have been logical and intuitive.
I get an exception
The specified table does not exist [Limits]
while I'm trying saving new item
(App.Current as App).context.Limits.InsertOnSubmit(new Limit() { Date = DateTime.Now, Value = inputLimit });//this works
(App.Current as App).context.SubmitChanges();//here I get exception
Also I get an error on this line:
var currentLimit = (App.Current as App).context.Limits.Where(l => l.Date.Date == DateTime.Now.Date).FirstOrDefault();
Here is a "model"
public class CalCounterContext:DataContext
{
public CalCounterContext(string connstring):base(connstring)
{
}
public Table<Limit> Limits;
public Table<Meal> Meals;
}
[Table]
public class Limit
{
[Column(IsPrimaryKey = true, IsDbGenerated = true, DbType = "Int NOT NULL IDENTITY", CanBeNull = false, AutoSync = AutoSync.OnInsert)]
public int Id { get; set; }
[Column]
public DateTime Date { get; set; }
[Column]
public int Value { get; set; }
}
Sometimes it works, sometimes, doesn't. What could be a reson of my problem?
This normally happens when you add a table in a later version of the database then what is being used. When you create your database context, check to see if it is up to date, and if not, update the database using the DatabaseSchemaUpdater class as described here. If it is just while you are creating the app, uninstall and re-install the app.
Also, I ran into a strange issue where intermittently I would get this error even once the app was in production without any reasoning. Often is occured when I would launch the app and then hit the home or back button to end it quickly. I ended up re-implementing the GetTable<> function used to instantiate my ITable variable in a base database class so that it would do a hard check to see if the table actually existed:
public Table<TEntity> VerifyTable<TEntity>() where TEntity : class
{
var table = GetTable<TEntity>();
try
{
// can call any function against the table to verify it exists
table.Any();
}
catch (DbException exception)
{
if (exception.Message.StartsWith("The specified table does not exist."))
{
var databaseSchemaUpdater = this.CreateDatabaseSchemaUpdater();
databaseSchemaUpdater.AddTable<TEntity>();
databaseSchemaUpdater.Execute();
}
else
{
throw;
}
}
return table;
}
I had the same intermittent error you had. Try removing the database from the device and installing the app again. I found my issue was being caused because I was making changes to the model and when I re-ran the app, I would get this error.
The basic problem...
I have a method which executes the following code:
IList<Gig> gigs = GetGigs().WithArtist(artistId).ToList();
The GetGigs() method gets Gigs from my database via LinqToSql...
So, when GetGigs().WithArtist(artistId).ToList() is executed I get the following exception:
Member access 'ListenTo.Shared.DO.Artist Artist' of 'ListenTo.Shared.DO.Act' not legal on type 'System.Collections.Generic.List`1[ListenTo.Shared.DO.Act]
Note that the extension function "WithArtist" looks like this:
public static IQueryable<Gig> WithArtist(this IQueryable<Gig> qry, Guid artistId)
{
return from gig in qry
where gig.Acts.Any(act => (null != act.Artist) && (act.Artist.ID == artistId))
orderby gig.StartDate
select gig;
}
If I replace the GetGigs() method with a method that constructs a collection of gigs in code (rather than from the DB via LinqToSQL) I do NOT get the exception.
So I'm fairly sure the problem is with my LinqToSQl code rather than the object structure.
However, I have NO IDEA why the LinqToSQl version isnt working, so I've included all the associated code below. Any help would be VERY gratefully receivced!!
The LinqToSQL code....
public IQueryable<ListenTo.Shared.DO.Gig> GetGigs()
{
return from g in DBContext.Gigs
let acts = GetActs(g.ID)
join venue in DBContext.Venues on g.VenueID equals venue.ID
select new ListenTo.Shared.DO.Gig
{
ID = g.ID,
Name = g.Name,
Acts = new List<ListenTo.Shared.DO.Act>(acts),
Description = g.Description,
StartDate = g.Date,
EndDate = g.EndDate,
IsDeleted = g.IsDeleted,
Created = g.Created,
TicketPrice = g.TicketPrice,
Venue = new ListenTo.Shared.DO.Venue {
ID = venue.ID,
Name = venue.Name,
Address = venue.Address,
Telephone = venue.Telephone,
URL = venue.Website
}
};
}
IQueryable<ListenTo.Shared.DO.Act> GetActs()
{
return from a in DBContext.Acts
join artist in DBContext.Artists on a.ArtistID equals artist.ID into art
from artist in art.DefaultIfEmpty()
select new ListenTo.Shared.DO.Act
{
ID = a.ID,
Name = a.Name,
Artist = artist == null ? null : new Shared.DO.Artist
{
ID = artist.ID,
Name = artist.Name
},
GigId = a.GigID
};
}
IQueryable<ListenTo.Shared.DO.Act> GetActs(Guid gigId)
{
return GetActs().WithGigID(gigId);
}
I have included the code for the Act, Artist and Gig objects below:
public class Gig : BaseDO
{
#region Accessors
public Venue Venue
{
get;
set;
}
public System.Nullable<DateTime> EndDate
{
get;
set;
}
public DateTime StartDate
{
get;
set;
}
public string Name
{
get;
set;
}
public string Description
{
get;
set;
}
public string TicketPrice
{
get;
set;
}
/// <summary>
/// The Act object does not exist outside the context of the Gig, therefore,
/// the full act object is loaded here.
/// </summary>
public IList<Act> Acts
{
get;
set;
}
#endregion
}
public class Act : BaseDO
{
public Guid GigId { get; set; }
public string Name { get; set; }
public Artist Artist { get; set; }
}
public class Artist : BaseDO
{
public string Name { get; set; }
public string Profile { get; set; }
public DateTime Formed { get; set; }
public Style Style { get; set; }
public Town Town { get; set; }
public string OfficalWebsiteURL { get; set; }
public string ProfileAddress { get; set; }
public string Email { get; set; }
public ImageMetaData ProfileImage { get; set; }
}
public class BaseDO: IDO
{
#region Properties
private Guid _id;
#endregion
#region IDO Members
public Guid ID
{
get
{
return this._id;
}
set
{
this._id = value;
}
}
}
}
I think the problem is the 'let' statement in GetGigs. Using 'let' means that you define a part of the final query separately from the main set to fetch. the problem is that 'let', if it's not a scalar, results in a nested query. Nested queries are not really Linq to sql's strongest point as they're executed deferred as well. In your query, you place the results of the nested query into the projection of the main set to return which is then further appended with linq operators.
When THAT happens, the nested query is buried deeper into the query which will be executed, and this leads to a situation where the nested query isn't in the outer projection of the query to execute and thus has to be merged into the SQL query ran onto the DB. This is not doable, as it's a nested query in a projection nested inside the main sql query and SQL doesn't have a concept like 'nested query in a projection', as you can't fetch a set of elements inside a projection in SQL, only scalars.
I had the same issue and what seemed to do the trick for me was separating out an inline static method call that returned IQueryable<> so that I stored this deferred query into a variable and referenced that.
I think this is a bug in Linq to SQL but at least there is a reasonable workaround. I haven't tested this out yet but my assumption is that this problem may arise only when referencing static methods of a different class within a query expression regardless of whether the return type of that function is IQueryable<>. So maybe it's the class that holds the method that is at the root of the problem. Like I said, I haven't been able to confirm this but it may be worth investigating.
UPDATE: Just in case the solution isn't clear I wanted to point it out in context of the example from the original post.
public IQueryable<ListenTo.Shared.DO.Gig> GetGigs()
{
var acts = GetActs(g.ID); // Don't worry this call is deferred
return from g in DBContext.Gigs
join venue in DBContext.Venues on g.VenueID equals venue.ID
select new ListenTo.Shared.DO.Gig
{
ID = g.ID,
Name = g.Name,
Acts = new List<ListenTo.Shared.DO.Act>(acts),
Description = g.Description,
StartDate = g.Date,
EndDate = g.EndDate,
IsDeleted = g.IsDeleted,
Created = g.Created,
TicketPrice = g.TicketPrice,
Venue = new ListenTo.Shared.DO.Venue {
ID = venue.ID,
Name = venue.Name,
Address = venue.Address,
Telephone = venue.Telephone,
URL = venue.Website
}
};
}
Note that while this should correct the issue at hand there also seems to be another issue in that the deferred acts query is being accessed in each element of the projection which I would guess would cause separate queries to be issued to the database per row in the outer projection.
I don't see anything in your classes to indicate how LINQ to SQL is meant to work out which column is which, etc.
Were you expecting the WithArtist method to be executed in .NET, or converted into SQL? If you expect it to be converted into SQL, you'll need to decorate your Gig class with appropriate LINQ to SQL attributes (or configure your data context some other way). If you want it to be executed in code, just change the first parameter type from IQueryable<Gig> to IEnumerable<Gig>.
I found out that an issue like this (which I also had recently) can be resolved, if you convert the IQueryable (or Table) variable Gigs into a list like so
return from g in DBContext.Gigs.ToList()
...
If that still doesn't work, do the same for all the IQueryables. The reason behind seems to me that some queries are too complex to be translated into SQL. But if you "materialize" it into a list, you can do every kind of query.
Be careful, you should add "filters" (where conditions) early because too much memory consumption can become a problem.