Currently I'm working on a project where we have a query builder - the user selects what data he wants, what is shown on the final report and a few filters. We are also using Entity Framework (Code First) and we need the name of every string property of some classes. E.g.:
Model Class
public class User {
public int Id { get; set; }
public string FullName { get; set; }
public string FullAddress { get; set; }
}
As of now, I'm getting every property name like so:
Property Filter
var propertyList = type.GetProperties()
.Where(prop => prop.PropertyType == typeof(string))
.Select(prop => prop.Name).ToList();
And it works nicely for any change we make to the database, but it's not easy to read for the user (especially if you consider we need to keep all the code in English, even tough we'll publish it for people who mostly only speak Portuguese).
What I need is to display "FullName" as "Nome Completo", "FullAddress" as "Endereço Completo", etc, and still be able to get the original name somehow.
One solution I thought of was making a static dictionary and update it as needed; it's easy to process with jQuery (two way dictionary made with a simple object) but it'll be a pain to maintain since the database can get really big.
Are there any better options than static dictionaries?
You can apply a DisplayAttribute to the properties and link it to a resource file with the friendly names in English and/or Portuguese. This is the same way that MVC works. When you need to get the friendly name you just need to call the GetName() method on the attribute to get the appropriate name in the current Thread Culture.
Model Class
// add reference to System.ComponentModel.DataAnnotations to your project
public class User
{
public int UserId { get; set; }
// pass the "key" of the resource entry and the name of the resource file
[Display(Name = "FullName", ResourceType = typeof(UserResources))]
public string FullName { get; set; }
[Display(Name = "FullAddress", ResourceType = typeof(UserResources))]
public string FullAddress { get; set; }
public string OtherProp { get; set; }
}
UserResources.resx
Default English version (you could just put the Portuguese in here if the website itself isn't truly "multi-lingual")
FullName Full Name
FullAddress Full Address
UserResources.pt-pt.resx
Portuguese translations
FullName Nome Completo
FullAddress Endereço Completo
Helper Method
This will retrieve the translated display name if a [DisplayAttribute] is present. If not, just the name of the property.
private static string GetPropertyName(PropertyInfo prop)
{
var displayAttribute = prop.GetCustomAttribute<DisplayAttribute>();
if (displayAttribute != null)
{
// GetName() fetches from the resource file of the current Thread Culture
return displayAttribute.GetName();
}
else
{
return prop.Name;
}
}
Sample Usage to get list of property names
public static void Main(string[] args)
{
// Uncomment to get the names in Portuguese
//Thread.CurrentThread.CurrentCulture = Thread.CurrentThread.CurrentUICulture = CultureInfo.GetCultureInfo("pt-PT");
Type type = typeof(User);
var propertyList = type.GetProperties()
.Where(prop => prop.PropertyType == typeof(string))
.Select(prop => GetPropertyName(prop)).ToList();
foreach (string propertyName in propertyList)
{
Console.WriteLine(propertyName);
}
}
The only other thing to note is that the resource file class is generated as an internal class by default and you will probably need to make it public. You can do this by setting the Custom Tool in the Properties window in Visual Studio to PublicResXFileCodeGenerator. Otherwise you may get an error saying "no public property FirstName found in resource file".
If you right click on a table, or a column, in SQL Server Management Studio, and select properties, you will see that there is an option for Extended Properties. You could add an extended property called Friendly Name for each column, then have a separate query to load your dictionary at the applications start.
Here is a query that will help you pull Extended Properties for columns in your database.
SELECT major_id, minor_id, t.name AS [Table Name], c.name AS [Column Name], value AS [Extended Property], ep.name as [Property Name]
FROM sys.extended_properties AS ep
INNER JOIN sys.tables AS t ON ep.major_id = t.object_id
INNER JOIN sys.columns AS c ON ep.major_id = c.object_id AND ep.minor_id = c.column_id
WHERE class = 1;
Example brazenly stolen from the following url (I make no pretense of having this stuff memorized):
http://technet.microsoft.com/en-us/library/ms186989(v=SQL.105).aspx
Related
Let's say we have a realm results taken with
RealmDb.All<Entry>();
Then I want to do some search over those results using not yet supported techniques, like StartsWith on a function return or on a property which is not mapped in realm etc, so I get a subset
IEnumerable<Entry> subset = bgHaystack;
var results = subset.Where(entry => entry.Content.ToLower().StartsWith(needle));
To get somehow these as part of RealmResults, I extract the entry ids like this:
List<int> Ids = new List<int>();
foreach (Entry entry in entries)
{
Ids.Add(entry.Id);
}
return Ids;
and finally I want to return a subset of RealmResults (not IEnumerable) of only those Entries that contain those ids, how can I do that? IDE says the Contains method is not supported.
Can I use some kind of predicate or a comparer for that?
Entry is my model class
using System.ComponentModel.DataAnnotations.Schema;
using Realms;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System;
namespace Data.Models
{
[Table("entry")]
public class Entry : RealmObject
{
public class EntryType
{
public const byte Word = 1;
public const byte Phrase = 2;
public const byte Text = 3;
};
[Key]
[PrimaryKey]
[Column("entry_id")]
public int Id { get; set; }
[Column("user_id")]
public int UserId { get; set; }
[Column("source_id")]
public int SourceId { get; set; }
[Indexed]
[Column("type")]
public byte Type { get; set; }
[Column("rate")]
public int Rate { get; set; }
[Column("created_at")]
public string CreatedAt { get; set; }
[Column("updated_at")]
public string UpdatedAt { get; set; }
[NotMapped]
public Phrase Phrase { get; set; }
[NotMapped]
public Word Word { get; set; }
[NotMapped]
public Text Text { get; set; }
[NotMapped]
public IList<Translation> Translations { get; }
[NotMapped]
public string Content
{
get {
switch (Type)
{
case EntryType.Phrase:
return Phrase?.Content;
case EntryType.Word:
return Word?.Content;
case EntryType.Text:
return Text?.Content;
}
return "";
}
}
}
}
According to the documentation, Realm .NET supports LINQ, so that's promising. In your specific example, you indicate that StartsWith isn't supported, but I see that on the above page, specifically here.
Now, your example makes clear that Entry is a RealmObject, so it's not clear where you'd possibly get a RealmResult from (nor does their documentation on that page mention a RealmResult). Specifically, the home page indicates that you're really only going to ever work with Realm, RealmObject and Transaction, so I'm going to just assume that you meant that you'll need a resulting RealmObject per their examples.
The way you presently have your data object set up, you're rather stuck calling it like you are (though if I could make a recommendation to simplify it a little bit:
var entries = RealmDb.All<Entry>().ToList();
var results = entries.Where(entry => entry.Content.ToLower().StartsWith(needle));
var ids = results.Select(a => a.Id).ToList();
Now, your big issue with just combining the filter predicate in line 2 with the end of line 1: Content itself is marked with a [NotMapped] attribute. Per the documentation again:
As a general rule, you can only create predicates with conditions that
rely on data in Realm. Imagine a class
class Person : RealmObject
{
// Persisted properties
public string FirstName { get; set; }
public string LastName { get; set; }
// Non-persisted property
public string FullName => FirstName + " " + LastName;
}
Given this class, you can create queries with conditions that apply to
the FirstName and LastName properties but not to the FullName
property. Likewise, properties with the [Ignored] attribute cannot be
used.
Because you're using [NotMapped], I've got to believe that's going to behave similarly to [Ignored] and further, because it's just a computed value, it's not something that Realm is going to be able to process as part of the query - it simply doesn't know it because you didn't map it to the information Realm is storing. Rather, you'll have to compute the Content property when you've actually got the instances of your Entry objects to enumerate through.
Similarly, I expect you'll have issues pulling values from Phrase, Word and Text since they're also not mapped, and thus not stored in the record within Realm (unless you're populating those in code you didn't post before executing your Where filter).
As such, you might instead consider storing separate records as a PhraseEntry, WordEntry, and TextEntry so you can indeed perform exactly that filter and execute it on Realm. What if you instead used the following?
public class Entry : RealmObject
{
[Key]
[PrimaryKey]
[Column("entry_id")]
public int Id { get; set; }
[Column("user_id")]
public int UserId { get; set; }
[Column("source_id")]
public int SourceId { get; set; }
[Column("rate")]
public int Rate { get; set; }
[Column("created_at")]
public string CreatedAt { get; set; }
[Column("updated_at")]
public string UpdatedAt { get; set; }
[Column("content")]
public string Content { get; set; }
[NotMapped]
public IList<Translation> Translations { get; }
}
[Table("wordEntry")]
public class WordEntry : Entry
{
}
[Table("phraseEntry")]
public class PhraseEntry : Entry
{
}
[Table("textEntry")]
public class TextEntry : Entry
{
}
And now, you can offload the filtering to Realm:
var wordEntries = RealmDb.All<WordEntry>.Where(entry =>
entry.Content.StartsWith(needle, StringComparison.OrdinalIgnoreCase)).ToList();
var phraseEntries = RealmDb.All<PhraseEntry>.Where(entry => entry.Content.StartsWith(needle, StringComparison.OrdinalIgnoreCase)).ToList();
var textEntries = RealmDb.All<TextEntry>.Where(entry => entry.Content.StartsWith(needle, StringComparison.OrdinalIgnoreCase)).ToList();
var entries = new List<Entry>();
entries.AddRange(wordEntries);
entries.AddRange(phraseEntries);
entries.AddRange(textEntries);
var ids = entries.Select(entry => entry.Id).ToList();
It's not quite as brief as storing it all in one table, but I'm not immediately seeing any Realm documentation that indicates support for executing the same query against multiple tables simultaneously, so at least this would allow you to leave the filtering to the database and work against a more limited subset of values locally.
Finally, so we have all that and I missed your final question up top. You indicate that you want to return a subset of your entries based on some collection of ids you create. In the logic you provide, you're retrieving all the Id properties in all your results, so there's really no further subset to pull.
That said, let's assume you have a separate list of ids that for whatever complicated reason, you were only able to derive after retrieving the list of Entry types from above (themselves all PhraseEntry, WordEntry or TextEntry objects).
At this point, since you've already pulled all the values from Realm and have them locally, just execute another Where statement against them. Because a List implements IEnumerable, you can thus execute the LINQ locally without any of the Realm restrictions:
var myLimitedIdSet = new List<int>()
{
10, 15, 20, 25 //Really complicated logic to narrow these down locally
};
var resultingEntries = entries.Where(entry => myLimitedIdSet.Contains(entry.Id)).ToList();
And you're set. You'll have only those entries that match the IDs listed in myLimitedIdSet.
Edit to address comment
You see this error because of the detail provided at the top of this page in the documentation. Specifically (and adapting to your code):
The first statement gives you a new instance of Entry of a class that implements IQueryable... This is standard LINQ implementation - you get an object representing the query. The query doesn't do anything until you made a further call that needs to iterate or count the results.
Your error is then derived by taking the result from RealmDb.All<Entry>() and trying to cast it to an IEnumerable<Entry> to operate against it as though you have local data. Until you call ToList() onRealmDb.All` you simply have a LINQ representation of what the call will be, not the data itself. As such, when you further refine your results with a Where statement, you're actually adding that to a narrowed version of the IQueryable statement, which will also fail because you lack the appropriate mapping in the Realm dataset.
To skip the optimization I provided above, the following should resolve your issue here:
var bgHaystack = realm.All<Entry>().ToList(); //Now you have local data
var results = bgHaystack.Where(entry => entry.Content.ToLower().StartsWith(needle));
Unfortunately, given your provided code, I don't expect that you'll see any matches here unless needle is an empty string. Not only is your Content property not part of the Realm data and you thus cannot filter on it within Realm, but neither are your Phrase, Word or Text properties mapped either. As a result, you will only ever see an empty string when getting your Content value.
You can further refine the results variable above to yield only those instances with a provided ID as you see fit with normal LINQ (as again, you'll have pulled the data from Realm in the first line).
var limitedIds = new List<int>{10, 20, 30};
var resultsLimitedById = results.Select(a => limitedIds.Contains(a.Id)).ToList();
I've updated my examples above to reflect the use of ToList() in the appropriate places as well.
I've just started using mongodb in c# and it's great however I'm struggling to understand how i could dynamically create a linq query to pass to mongodb.
Situation: I have a file that has some general properties filename, filesize ect, one of these properties is metadata, which is a list of fields with values. the user will be able to specify the search criteria dynamically and so i cant hard code this query.
My Object for completeness:
public class asset
{
public ObjectId Id { get; set; }
public string filename { get; set; }
public int filesize { get; set; }
public List<shortmetadata> metadata { get; set; }
}
public class shortmetadata
{
public string id { get; set; }
public string value { get; set; }
}
My current code which is manually setting the search criteria and returns any asset that has "hello" or "world" in the metadata value field:
MongoClient client = new MongoClient();
var db = client.GetDatabase("Test");
var collection = db.GetCollection<asset>("assets");
var assets = collection.AsQueryable().Where(i =>
i.metadata.Any(m => m.value.Contains("hello")) ||
i.metadata.Any(m => m.value.Contains("world"))
);
What i would like to be able to do is dynamically create the query based on the users selection (don't have this yet as want to get it working in code first!)
Any help would be great.
If, for example, you had a Dictionary<string, string> containing the name value to search for keyed by the name of the meta item you could build your IQueryable<Asset> up in a loop like this
var query = collection.AsQueryable();
//Non-meta properties
query = query.Where(a => a.SomeNonMetaProperty == "Something");
//And now meta properties
foreach(var keyAndValue in someDictionary)
{
query = query.Where(m =>
m.Name == keyAndValue.Key
&& m.Value == keyAndValue.Value;
}
Slazure lets you create dynamic Linq queries at runtime since its predicates are string literals.
PM> Install-Package Slazure.MongoDB
// C# example: Build a document query that return employees that has a salary greater than $40k/year using a dynamic LINQ query filter.
dynamic storage = new QueryableStorage<DynDocument>("mongodb://user:pass#example.org/MongoDBExample");
QueryableCollection<DynDocument> employeesCollection = storage.Employees;
var employeeQuery = employeesCollection
// Query for salary greater than $40k and born later than early '95.
.Where("Salary > 40000 and Birthdate >= DateTime(1995,15,3)")
// Projection and aliasing.
.Select("new(_id as Email, Birthdate, Name, Timestamp as RegisteredDate)")
// Order result set by birthdate descending.
.OrderBy("Birthdate desc")
// Paging: Skip the first 5 and retrieve only 5.
.Skip(5).Take(5)
// Group result set on Birthdate and then on Name.
.GroupBy("Birthdate", "Name");
// Use a dynamic type so that we can get access to the document's dynamic properties
foreach (dynamic employee in employeeQuery)
{
// Show some information about the employee
Console.WriteLine("The employee '{0}' was employed {1} and was born in {2}.",
employee.Email, employee.RegisteredDate, employee.Birthdate.Year);
}
It also supports substitution values which makes your predicate code look cleaner.
// C# example: Query the storage for employee that earn less than $60k/yr and that are born before the millennium.
var amount = 60000;
var employeeQuery = employeesTable.Where("Salary > #0 and Timestamp <= #1", amount, new DateTime(2000, 1, 1));
I've got a small integration service which recieves XML files and parses it.
Also I've created classes from provided XSD for deserializing XML data. During parsing I need to copy properties from those XSD-generated classes to my own that I use in Data Layer. This is an example of my aproach
var supplierInfo = new SupplierInfo();
//coping properties
supplierInfo.Name = supplier.name;
supplierInfo.ShortName = supplier.shortName;
supplierInfo.BrandName = supplier.brandName;
supplierInfo.AdditionalFullName = supplier.additionalFullName;
supplierInfo.AdditionalCode = supplier.additionalCode;
supplierInfo.AdditionalInfo = supplier.additionalInfo;
//lot's of other properties
//...
supplierInfo.Tax = supplier.tax;
supplierInfo.RegistrationDate = supplier.registrationDate;
Some times ammount of properties is very big. Is there more eligant way to copy those properties?
Automapper has been out there since ages ago. Tried and tested. http://automapper.org/
Here's an example:
using System;
using AutoMapper;
public class Program
{
class SupplierInfo
{
public SupplierInfo( string name, string shortName, string brandName ) {
Name = name;
ShortName = shortName;
BrandName = brandName;
}
public string Name {get; private set; }
public string ShortName {get; private set; }
public string BrandName {get; private set; }
}
class Supplier
{
public string name {get; set; }
public string shortName {get; set; }
public string brandName {get; set; }
}
public static void Main()
{
var dto = new Supplier() {
name = "Name 1",
shortName = "Short Name 1",
brandName = "Brand Name 1"
};
//From the tutorial:
//You only need one MapperConfiguration instance typically per AppDomain and should be instantiated during startup.
var config = new MapperConfiguration(cfg => cfg.CreateMap<Supplier, SupplierInfo>());
var mapper = config.CreateMapper();
SupplierInfo info = mapper.Map<SupplierInfo>(dto);
Console.WriteLine( info.Name );
Console.WriteLine( info.ShortName );
Console.WriteLine( info.BrandName );
}
}
The official Getting Started guide can be found at https://github.com/AutoMapper/AutoMapper/wiki/Getting-started
I am happy to be corrected on this but I always find automapper (as per the other answer), which maps property values by name/convention, a little scary to use in production code.
I don't really have a decent alternative but I prefer to do it manually as per your code sample - it's easier to read and debug and if you end up renaming any properties in a class, it will be clear that the copying code is broken (or if you use some IDE tool to rename the property, it'll change the copy code accordingly).
First, install EntityLite.Core:
PM> Install-Package EntityLite.Core
Then use it:
using inercya.EntityLite.Extensions;
...
supplierInfo.AssignPropertiesFrom(supplier);
EntityLite is a micro ORM I developed. It has some little gems :-)
EDIT:
I guess you may not want to install EntityLite.Core just to copy some properties from an object to another. So here you have an implementation of AssignPropertiesFrom extension method that uses Reflection:
public static class ObjectExtensions
{
public static void AssignPropertiesForm(this object target, object source)
{
if (target == null || source == null) throw new ArgumentNullException();
var targetPropertiesDic = target.GetType().GetProperties().Where(p => p.CanWrite).ToDictionary(p => p.Name, StringComparer.CurrentCultureIgnoreCase);
foreach (var sourceProp in source.GetType().GetProperties().Where(p => p.CanRead))
{
PropertyInfo targetProp;
if (targetPropertiesDic.TryGetValue(sourceProp.Name, out targetProp))
{
targetProp.SetValue(target, sourceProp.GetValue(source, null), null);
}
}
}
}
Incidentally, this is not the EntityLite implementation. EntityLite uses dynamic IL generation.
I have a simple database with two tables: Photo and Tag. There is a one-to-many (a photo can have many tags) relationship between the two tables. Here is a diagram:
Now I have made a Photo class and set it up for LINQ-to-SQL using attributes. The code for that class is below:
[Table]
public class Photo
{
[Column(IsDbGenerated = true, IsPrimaryKey = true, CanBeNull = false)]
public int ID { get; set; }
[Column(CanBeNull = false)]
public string Filename { get; set; }
[Column(CanBeNull = false)]
public string Description { get; set; }
[Column(CanBeNull = false)]
public DateTime DateTaken { get; set; }
public List<string> Tags { get; set; }
public override string ToString()
{
string result = String.Format("File: {0}, Desc: {1}, Date: {2}, Tags: ",
Filename, Description, DateTaken);
if (Tags != null)
foreach (string tag in Tags)
result += tag + ", ";
return result;
}
}
You will notice that currently I do not have any attributes for the Tags list. I would like to be able to setup the attributes (associations) for the Tags list so that it would be populated with Name field of the Tag table for all entries in the Tag table of a particular PhotoID. It would be preferable if I could do this directly (i.e. without having to setup a Tag class mimicking/relating to the Tag table). Since I'm only interested in one field (the Name in the Tag table) rather than many fields, I would think there is a way to do this.
Is this possible, and if so how would I further decorate the class with attributes and what would be the syntax for a simiple Select query using LINQ-to-SQL?
If it helps, here is the code I am using to simply add a new photo and then grab all of the photos out of the database (obviously the tag information is not pulled out as the code stands now).
DataContext context = new DataContext(connectionString);
// add new photo
Photo newPhoto = new Photo { Filename = "MyImage1.jpg", Description = "Me", DateTaken = DateTime.Now };
context.GetTable<Photo>().InsertOnSubmit(newPhoto);
context.SubmitChanges();
// print out all photos
var photoQuery = from m in context.GetTable<Photo>() select m;
foreach (Photo myPhoto in photoQuery)
textBox1.Text += Environment.NewLine + myPhoto.ToString();
First I'd suggest you to use a tool to generate your entity classes (the classes that correspond to the database tables). We'r using sqlmetal and it does the job very well.
Next, (if you have a Tag entity) than write a function that fetches the tags for some photos:
void GetTags(IEnumerable<Photo> photos)
{
var ids = photos.Select(p=>p.ID).ToList();
var tagsG = (from tag in context.GetTable<Tag>() where ids.Contains(tag.PhotoID) select new {PhotoID, Name}).GroupBy(tag=>tag.PhotoID);
foreach(ph in photos){
ph.Tags = tagsG[ph.ID].Select(tag=>tag.Name).ToList();
}
}
Note, the code might not compile I've written it in the browser...
You should refer to the Attribute Based Mapping article on msdn.
Also, this article shows how to decorate an EntitySet property with an Association attribute to accomplish the relationship modeling.
It would be preferable if I could do this directly (i.e. without having to setup a Tag class mimicking/relating to the Tag table).
Not possible. LinqToSql needs to know what is or isn't a table, so it can generate the proper sql text.
What you can do instead, is make one set of types for representing database structure, and another set of types for use elsewhere in your program. The second set of types could have a single class representing Photo and Tag data.
Write a query with the first set of types, then use them to construct instances of the second set.
I'm in charge to migrate our own DAL to a solution based on Entity Framework 4 but, before I can do it, I need to be sure it's possible to translate all our "constructs" to this new technology.
One of the biggest issues I'm having is the possibility to read a field and build a custom type. Valid examples could be a bit mask saved in a BIGINT field, a list of mail addresses saved as a CSV list in a NVARCHAR field or an XML field containing aggregated data not worth to have their own table/entity. Basically the serialization mechanism is not fixed.
Let's take the classic "Address" example.
public class Address
{
public string Street {get; set;}
public string City {get; set;}
public string Zip {get; set;}
public string Country {get; set;}
}
and let's suppose we want to save it in an XML field using this template:
<address>
<street>Abrahamsbergsvägen, 73</street>
<city>Stockholm</city>
<zip>16830</zip>
<country>Sweden</country>
</address>
The question basically is: does exist a method to override how EF4 serializes and deserializes the content of a field mapped to a property of an entity?
I found this solution. It's not as clean as I wished but it seems it's impossible to get anything better.
given this base entity,
public class Institute
{
public int InstituteID { get; set; }
public string Name { get; set; }
// other properties omitted
}
I added in the database an XML field called Data containing some strings using this simple template
<values>
<value>Value 1</value>
<value>Value 2</value>
<value>Value 3</value>
</values>
In the entity I added these properties and I mapped the database field "Data" to the property "DataRaw".
protected string DataRaw
{
get
{
if (_Data == null)
return _DataRaw;
else
return new XElement("values", from s in Data select new XElement("value", s)).ToString();
}
set
{
_DataRaw = value;
}
}
private string _DataRaw;
private string[] _Data;
public string[] Data
{
get
{
if (_Data == null)
{
_Data = (from elem in XDocument.Parse(_DataRaw).Root.Elements("value")
select elem.Value).ToArray();
}
return _Data;
}
set
{
_Data = value;
}
}
This solution works. Here is the sample code:
class Program
{
static void Main(string[] args)
{
var ctx = new ObjectContext("name=TestEntities");
var institute = ctx.CreateObjectSet<Institute>().First();
System.Console.WriteLine("{0}, {1}", institute.InstituteID, institute.Name);
foreach (string data in institute.Data)
System.Console.WriteLine("\t{0}", data);
institute.Data = new string[] {
"New value 1",
"New value 2",
"New value 3"
};
ctx.SaveChanges();
}
}
Does anyone have a better solution?
Entity Framework does NOT serializes or deserializes entities nor it controls how the serialization should take place in other layers or modules of your application.
What you need to do is to simply open your POCO(s) and annotate their Properties with appropriate attributes that will be taken into account at the time of serialization when you want to ship them to your other application layers.