I think I'm just searching for the wrong terms, since I can't seem to find an answer to what I'm fairly sure is a simple question.
I have two classes/mappings (simplified);
public class Applications
{
public int Id {get; set;}
public string Name {get; set;}
public ApplicationType {get; set;}
public IEnumerable<ApplicationProperty> ApplicationProperties {get; set;}
}
public class ApplicationProperties
{
public int Id {get; set;}
public int Application_Id {get; set}
public string Value {get; set;}
}
I'm trying to build up a Criteria class in a (possibly misguided) attempt to make our code more readable/reusable, as follows;
public static class ApplicationsQuery
{
public static ICriteria GetQuery(ISession session)
{
return session.CreateCriteria(typeof(Application));
}
public static ICriteria WithType(this ICriteria crit, ApplicationType type)
{
crit.Add(
Restrictions.Eq(
Projections.ProjectionList().Add(
Projections.Property<Application>(a => a.ApplicationType)), type));
return crit;
}
public static ICriteria WithProperties(this ICriteria crit)
{
// What goes here?!
}
}
So that I can do something like
ICriteria query = ApplicationsQuery.GetQuery(session).WithType(ApplicationType.GameServer).WithProperties();
I've tried various things such as;
DetachedCriteria properties =
DetachedCriteria.For<Application>()
.SetProjection(Projections.Property<Application>(a => a.ApplicationProperties));
return crit.Add(Subqueries.Select(properties));
// Or this
return crit.SetFetchMode("ApplicationProperties", FetchMode.Eager);
But I'm unable to get the ApplicationProperties to be populated.
My test setup looks like this;
session.Save(new Application("Test Application 1", ApplicationType.GameServer), 1);
session.Save(new Application("Test Application 2", ApplicationType.Manager), , 2);
session.Save(new ApplicationProperty(1, "Test Property"), 1);
EDIT
Adding in the mappings as I get the feeling that there might be an issue with them.
public class ApplicationMapping : ClassMap<Application>
{
public ApplicationMapping()
{
Table("Applications");
Id(o => o.Id, "Application_Id").GeneratedBy.Assigned();
Map(o => o.Name).Column("Logical_Name");
Map(o => o.ApplicationType).Column("Application_Type").CustomType<ApplicationType>();
HasMany(o => o.ApplicationProperties).KeyColumn("Application_Id").ReadOnly().Cascase.None();
}
}
public class ApplicationPropertyMapping : ClassMap<ApplicationProperty>
{
public ApplicationPropertyMapping()
{
Table("Application_Properties");
Id(o => o.Id).GeneratedBy.Identity().Column("Property_Id");
Map(o => o.ApplicationId).Column("Application_Id");
Map(o => o.Value).Column("Property_Value");
}
}
Update: i stripped down the code
public class ApplicationsQueryBuilder
{
private static readonly IProjection ApplicationTypeProperty = Projections.Property<Application>(a => a.ApplicationType);
private readonly DetachedCriteria _query = DetachedCriteria.For<Application>();
private bool _withProperties;
private bool _filteredByCollection;
public ApplicationsQueryBuilder WithType(ApplicationType type)
{
_query.Add(Restrictions.Eq(ApplicationTypeProperty, type));
return this;
}
public ApplicationsQueryBuilder WithTypes(params ApplicationType[] types)
{
var or = Restrictions.Disjunction();
foreach (var type in types)
{
or.Add(Restrictions.Eq(ApplicationTypeProperty, type));
}
_query.Add(or);
return this;
}
public ApplicationsQueryBuilder WithProperties()
{
_withProperties = true;
return this;
}
public ApplicationsQueryBuilder WithProperty(string name)
{
_query.CreateCriteria("ApplicationProperties")
.Add(Restrictions.Eq("Name", name));
_filteredByCollection = true;
return this;
}
...
public ICriteria Create(ISession session)
{
if (_withProperties && _filteredByCollection)
{
_query.SetProjection(Projections.Id());
return session.CreateCriteria<Application>()
.SetFetchMode("ApplicationProperties", FetchMode.Eager);
.Add(Subqueries.PropertyIn("Id", _query));
}
else if (_withProperties)
{
return _query.GetExecutableCriteria(_session)
.SetFetchMode("ApplicationProperties", FetchMode.Eager);
}
else
{
return _query.GetExecutableCriteria(session);
}
}
}
Related
I have the following classes:
public class Person
{
[JsonProperty("name")]
public string Name { get; set; }
[JsonProperty("age")]
public int Age { get; set; }
[JsonProperty("country")]
public string Country { get; set; }
[JsonProperty("profession")]
public Profession Profession { get; set; }
[JsonProperty("hobbies")]
public List<string> Hobbies { get; set; }
}
public class Profession
{
[JsonProperty("name")]
public string ProfessionName { get; set; }
[JsonProperty("industry")]
public string Industry { get; set; }
[JsonProperty("salary")]
public string AverageSalary { get; set; }
[JsonProperty("activities")]
public List<WorkActivity> WorkActivities { get; set; }
}
public class WorkActivity
{
[JsonProperty("id")]
public int Id { get; set; }
[JsonProperty("rooms")]
public List<string> Rooms { get; set; }
}
public class PropertiesVisitor : ExpressionVisitor
{
private readonly Expression param;
public List<string> Names { get; } = new List<string>();
public PropertiesVisitor(Expression parameter)
{
param = parameter;
}
protected override Expression VisitMember(MemberExpression node)
{
if (node.Expression == param)
{
Names.Add(node.Member.GetCustomAttribute<JsonPropertyAttribute>().PropertyName);
}
return base.VisitMember(node);
}
}
I call the methods in my app like this:
private static List<string> FindPropertyNames<T>(Expression<Func<T, object>> e)
{
var visitor = new PropertiesVisitor(e.Parameters[0]);
visitor.Visit(e);
return visitor.Names;
}
public static void Main(string[] args)
{
var names = FindPropertyNames<Person>(x => new { x.Age, x.Country, x.Profession.AverageSalary, x.Hobbies });
Console.WriteLine(string.Join(" ", names));
}
It works fine, except for one minor detailed - it doesn't check for nested properties. The output is the following: age country profession hobbies. I want it to be age country profession.salary hobbies.
I've been trying to fix the issue using a different approach, but I am unable to do so fully. I've tried the following:
public static MemberExpression GetMemberExpression(Expression e)
{
if (e is MemberExpression)
{
return (MemberExpression)e;
}
else if (e is LambdaExpression)
{
var le = e as LambdaExpression;
if (le.Body is MemberExpression)
{
return (MemberExpression)le.Body;
}
else if (le.Body is UnaryExpression)
{
return (MemberExpression)((UnaryExpression)le.Body).Operand;
}
}
return null;
}
public static string GetPropertyPath<T>(Expression<Func<T, object>> expr)
{
var path = new StringBuilder();
MemberExpression me = GetMemberExpression(expr);
do
{
if (path.Length > 0)
{
path.Insert(0, ".");
}
path.Insert(0, me.Member.GetCustomAttribute<JsonPropertyAttribute>().PropertyName);
me = GetMemberExpression(me.Expression);
}
while (me != null);
return path.ToString();
}
It kind of does the job - but it can't take more than one property.
I call it like this:
var x = GetPropertyPath<Person>(p => p.Profession.AverageSalary);
Console.WriteLine(x);
I want to be able to send multiple properties, as in the first version. Also, I am unsure how to pass the following person.Profession.WorkActivities.Rooms as a parameter, because it is a list. I want to get profession.activities.rooms as output for it.
I would write a method that takes an Expression and returns all the members in the chain:
public static IEnumerable<MemberExpression> MemberClauses(this Expression expr) {
if (expr is not MemberExpression mexpr) {
yield break;
}
foreach (var item in MemberClauses(mexpr.Expression)) {
yield return item;
}
yield return mexpr;
}
Then, you can unwrap an entire method chain and LINQ to get the JSON property names:
public class PropertiesVisitor : ExpressionVisitor {
private readonly Expression param;
public List<string> Names { get; } = new List<string>();
public PropertiesVisitor(Expression parameter) => param = parameter;
[return: NotNullIfNotNull("node")]
public override Expression Visit(Expression node) {
var chain = node.MemberClauses().ToList();
if (chain.Any() && chain.First().Expression == param) {
var name = string.Join(".", chain.Select(
mexpr => mexpr.Member.GetCustomAttribute<JsonPropertyAttribute>().PropertyName
));
Names.Add(name);
return node;
} else {
return base.Visit(node);
}
}
}
and you can then get the property path as follows:
public static class Functions {
public static List<string> GetPropertyPath<T>(Expression<Func<Person, T>> expr) {
var visitor = new PropertiesVisitor(expr.Parameters[0]);
visitor.Visit(expr);
return visitor.Names;
}
}
var names = Functions.GetPropertyPath(p => new { p.Age, p.Country, p.Profession.AverageSalary, p.Hobbies });
foreach (var name in names) {
Console.WriteLine(name);
}
During a runtime mapping operation (like when you use ResolveUsing or a custom TypeConverter) is it possible to get the container classes (or types at least) of the source and destination members?
I know that when you map one object to another, that the objects don't have to be members of some "parent" or "container" object, but I'm talking about the situation when AutoMapper is recursively copying a complex object.
Here's an example:
Here I'm copying (or setting it up at least) Cars & Boats of "kind A" to "kind B".
public class VehicleCopyProfile : AutoMapper.Profile
{
public VehicleCopyProfile()
{
this.CreateMap<CarA, CarB>();
this.CreateMap<BoatA, BoatB>();
this.CreateMap<WindshieldA, WindshieldB>(
.ConvertUsing((s, d, resContext) =>
{
// *** How can I tell if s is coming from a Car or a Boat? ***
});
}
}
// Cars & Boats each have a Windshield
public class CarA
{
public WindshieldA Windshield {get;set;}
}
public class BoatA
{
public WindshieldA Windshield {get;set;}
}
public class WindshieldA
{
public string Name {get;set;}
}
public class CarB
{
public WindshieldB Windshield {get;set;}
}
public class BoatB
{
public WindshieldB Windshield {get;set;}
}
public class WindshieldB
{
public string Name {get;set;}
}
Here is a solution using AutoMapper ResolutionContext Items as proposed by #Lucian Bargaoanu in comment. The idea is to use Before and After Map to store information in the Resolution Context. I use a Stack to keep track of the whole chain of relationship.
namespace SO51101306
{
public static class IMappingExpressionExtensions
{
public static IMappingExpression<A, B> RegisterChainOfTypes<A, B>(this IMappingExpression<A, B> mapping)
{
mapping.BeforeMap((a, b, ctx) => {
ctx.PushTypeInChainOfTypes(typeof(A));
});
mapping.AfterMap((a, b, ctx) => {
ctx.PopLastTypeInChainOfTypes();
});
return mapping;
}
}
public static class ResolutionContextExtensions
{
const string chainOfTypesKey = "ChainOfTypes";
private static Stack<Type> GetOrCreateChainOfTypesStack(ResolutionContext ctx)
{
var hasKey = ctx.Items.ContainsKey(chainOfTypesKey);
return hasKey ? (Stack<Type>)ctx.Items[chainOfTypesKey] : new Stack<Type>();
}
public static void PushTypeInChainOfTypes(this ResolutionContext ctx, Type type)
{
var stack = GetOrCreateChainOfTypesStack(ctx);
stack.Push(type);
ctx.Items[chainOfTypesKey] = stack;
}
public static Type PopLastTypeInChainOfTypes(this ResolutionContext ctx)
{
var stack = (Stack<Type>)ctx.Items[chainOfTypesKey];
return stack.Pop();
}
public static bool HasParentType(this ResolutionContext ctx, Type parentType)
{
var stack = GetOrCreateChainOfTypesStack(ctx);
return stack.Contains(parentType);
}
}
public class CarCopyProfile : Profile
{
public CarCopyProfile()
{
CreateMap<CarA, CarB>().RegisterChainOfTypes();
CreateMap<BoatA, BoatB>().RegisterChainOfTypes();
CreateMap<WindshieldA, WindshieldB>()
.ConvertUsing((wa,wb,ctx)=> {
if(ctx.HasParentType(typeof(CarA)))
{
Console.WriteLine("I'm coming from CarA");
//Do specific stuff here
}
else if (ctx.HasParentType(typeof(BoatA)))
{
Console.WriteLine("I'm coming from boatA");
//Do specific stuff here
}
return wb;
});
}
}
public class CarA
{
public WindshieldA Windshield { get; set; }
}
public class BoatA
{
public WindshieldA Windshield { get; set; }
}
public class CarB
{
public WindshieldB Windshield { get; set; }
}
public class BoatB
{
public WindshieldB Windshield { get; set; }
}
public class WindshieldA
{
public string Name { get; set; }
}
public class WindshieldB
{
public string Name { get; set; }
}
class Program
{
static void Main(string[] args)
{
Mapper.Initialize(c => c.AddProfile<CarCopyProfile>());
var carA = new CarA{Windshield = new WindshieldA()};
var boatA = new BoatA{Windshield = new WindshieldA()};
var carB = Mapper.Map<CarB>(carA);
var boatB = Mapper.Map<BoatB>(boatA);
}
}
}
This will output:
I'm coming from CarA
I'm coming from boatA
Another way is to use custom value resolver:
class CustomResolver<T1, T2>:IValueResolver ... { ... }
this.CreateMap<CarA, CarB>()
.ForMember(x => x.Windshield , opt => opt.ResolveUsing(new CustomResolver<CarA, CarB>()));
Then in you CustomResolver implementation:
var windshieldB = Mapper.Map<WindshieldB>(windshieldA, x => {x.Items["type1"] = typeof(T1); x.Items["type2"] = typeof(T2);});
And then:
this.CreateMap<WindshieldA, WindshieldB>(
.ConvertUsing((s, d, resContext) =>
{
// resContext.Options.Items["type1"]
});
See http://docs.automapper.org/en/stable/Custom-value-resolvers.html
I am having issues with hydrating a class which consists of a composite ID which in turn has a base class, I am getting an error saying InvalidOperationException: {document}.Identity is not supported.
The class i am trying to write to the database is below:
public class Product : IEntity<Product>
{
public readonly Sku Sku;
public string Name { get; private set; }
public string Description { get; private set; }
public bool IsArchived { get; private set; }
public Identity<Product> Identity => Sku;
public Product(Sku sku, string name, bool isArchived)
{
Sku = sku;
Name = name;
IsArchived = isArchived;
}
}
public interface IEntity<T>
{
Identity<T> Identity { get; }
}
In turn has an ID Sku which is a class formed of the below composite values (VendorId and a local Value within Sku):
public class Sku : Identity<Product>
{
public readonly VendorId VendorId;
public readonly string Value;
public Sku(VendorId vendorId, string value)
{
VendorId = vendorId;
Value = value;
}
protected override IEnumerable<object> GetIdentityComponents()
{
return new object[] {VendorId, Value};
}
}
public class VendorId : Identity<Vendor>
{
public readonly string Value;
public VendorId(string value)
{
Value = value;
}
protected override IEnumerable<object> GetIdentityComponents()
{
return new object[] {Value};
}
}
I have a base class for my entities Identity which i use in my DDD libraries, essentially the ToString() output here could be used as the ID if this would simplify things:
public abstract class Identity<T> : IEquatable<Identity<T>>
{
public override bool Equals(object obj) { /* snip */ }
public bool Equals(Identity<T> other) { /* snip */ }
public override int GetHashCode() { /* snip */ }
public override string ToString()
{
var id = string.Empty;
foreach (var component in GetIdentityComponents())
{
if (string.IsNullOrEmpty(id))
id = component.ToString(); // first item, dont add a divider
else
id += "." + component;
}
return id;
}
protected abstract IEnumerable<object> GetIdentityComponents();
}
I register the mappings on app start:
// rehydrate readonly properties via matched constructor
// https://stackoverflow.com/questions/39604820/serialize-get-only-properties-on-mongodb
ConventionRegistry
.Register(nameof(ImmutablePocoConvention), new ConventionPack { new ImmutablePocoConvention() }, _ => true);
BsonClassMap.RegisterClassMap<Product>(cm =>
{
cm.AutoMap();
cm.MapIdMember(c => c.Sku);
});
BsonClassMap.RegisterClassMap<Vendor>(cm =>
{
cm.AutoMap();
cm.MapIdMember(c => c.Id);
});
However when i go and write, i get InvalidOperationException: {document}.Identity is not supported.
// my respositoru method
public void Upsert<T>(T entity) where T : IEntity<T>
{
this.Database
.GetCollection<T>(product.GetType().FullName)()
.ReplaceOneAsync(x=>x.Identity.Equals(entity.Identity), entity, new UpdateOptions() {IsUpsert = true})
.Wait();
}
var product = new Product(new Sku(new VendorId("dell"), "12434" ),"RAM", false );
myProductRepo.Upsert(product);
Not sure if this is now overly complicated by me persisting direct from my entities layer (or if i just use an automapper and simpler POCO)... or if I am missing some mapping directives.
Appreciate any help or pointers.
I was looking at the hydration via constructor post which is done through GetProperties.
So public readonly Sku Sku; doesn't show up through classMap.ClassType.GetTypeInfo().GetProperties(_bindingFlags) because it is only can be accessed as member field.
You can change it to public Sku Sku { get; } so it is hydrated through constructor via GetProperties and change all the readonly fields (Sku - VendorId, Value & VendorId - Value fields) to have property getter method.
Also, You've to add cm.MapProperty(c => c.Identity) so x=>x.Identity.Equals(entity.Identity) can be serialized when used as expression because Identity cannot be hydrated and registered through ImmutablePocoConventionas it is not a constructor arg when automap logic runs.
Code changes:
public class Sku : Identity<Product>
{
public VendorId VendorId { get; }
public string Value { get; }
}
public class VendorId : Identity<Vendor>
{
public string Value { get; }
}
BsonClassMap.RegisterClassMap<Product>(cm =>
{
cm.AutoMap();
cm.MapIdMember(c => c.Sku);
cm.MapProperty(c => c.Identity);
});
Here is the code i used:
public class ProductMongoRepository : IProductRepository
{
public ICollection<Product> SearchBySkuValue(string sku)
{
return ProductsMongoDatabase.Instance.GetEntityList<Product>();
}
public Product GetBySku(Sku sku)
{
var collection = ProductsMongoDatabase.Instance.GetCollection<Product>();
return collection.Find(x => x.Sku.Equals(sku)).First();
}
public void SaveAll(IEnumerable<Product> products)
{
foreach (var product in products)
{
Save(product);
}
}
public void Save(Product product)
{
var collection = ProductsMongoDatabase.Instance.GetCollection<Product>();
collection
.ReplaceOneAsync(
x => x.Sku.Equals(product.Sku),
product,
new UpdateOptions() { IsUpsert = true })
.Wait();
}
}
Setting up the mapping here and support for readonly fields via constructor, for more complex scenarios and manual POCO mapping we could use BsonSerializer.RegisterSerializer(typeof(DomainEntityClass), new CustomerSerializer());
public sealed class ProductsMongoDatabase : MongoDatabase
{
private static volatile ProductsMongoDatabase instance;
private static readonly object SyncRoot = new Object();
private ProductsMongoDatabase()
{
BsonClassMap.RegisterClassMap<Sku>(cm =>
{
cm.MapField(c => c.VendorId);
cm.MapField(c => c.SkuValue);
cm.MapCreator(c => new Sku(new VendorId(c.VendorId.VendorShortname), c.SkuValue));
});
BsonClassMap.RegisterClassMap<VendorId>(cm =>
{
cm.MapField(c => c.VendorShortname);
cm.MapCreator(c => new VendorId(c.VendorShortname));
});
BsonClassMap.RegisterClassMap<Product>(cm =>
{
cm.AutoMap();
cm.MapIdMember(c => c.Sku);
cm.MapCreator(c => new Product(c.Sku, c.Name, c.IsArchived));
});
BsonClassMap.RegisterClassMap<Vendor>(cm =>
{
cm.AutoMap();
cm.MapIdMember(c => c.Id);
cm.MapCreator(c => new Vendor(c.Id, c.Name));
});
}
public static ProductsMongoDatabase Instance
{
get
{
if (instance != null)
return instance;
lock (SyncRoot)
{
if (instance == null)
instance = new ProductsMongoDatabase();
}
return instance;
}
}
}
The above implementation (which is a singleton) derives from the below base (any queries or writes are done in the parent implementation):
public abstract class MongoDatabase
{
private readonly IConfigurationRepository _configuration;
private readonly IMongoClient Client;
private readonly IMongoDatabase Database;
protected MongoDatabase()
{
//_configuration = configuration;
var connection = "mongodb://host:27017";
var database = "test";
this.Client = new MongoClient();
this.Database = this.Client.GetDatabase(database);
}
public List<T> GetEntityList<T>()
{
return GetCollection<T>()
.Find(new BsonDocument()).ToList<T>();
}
public IMongoCollection<T> GetCollection<T>()
{
return this.Database.GetCollection<T>(typeof(T).FullName);
}
}
My Sku domain model:
public class Sku : Identity<Product>
{
public readonly VendorId VendorId;
public readonly string SkuValue;
public Sku(VendorId vendorId, string skuValue)
{
VendorId = vendorId;
SkuValue = skuValue;
}
protected override IEnumerable<object> GetIdentityComponents()
{
return new object[] {VendorId, SkuValue};
}
}
My Product domain model:
public class Product : IEntity<Product>
{
public readonly Sku Sku;
public string Name { get; private set; }
public bool IsArchived { get; private set; }
public Product(Sku sku, string name, bool isArchived)
{
Sku = sku;
Name = name;
IsArchived = isArchived;
}
public void UpdateName(string name)
{
Name = name;
}
public void UpdateDescription(string description)
{
Description = description;
}
public void Archive()
{
IsArchived = true;
}
public void Restore()
{
IsArchived = false;
}
// this is used by my framework, not MongoDB
public Identity<Product> Identity => Sku;
}
My VendorID:
public class VendorId : Identity<Vendor>
{
public readonly string VendorShortname;
public VendorId(string vendorShortname)
{
VendorShortname = vendorShortname;
}
protected override IEnumerable<object> GetIdentityComponents()
{
return new object[] {VendorShortname};
}
}
Then i have my entity and identity types:
public interface IEntity<T>
{
Identity<T> Identity { get; }
}
public abstract class Identity<T> : IEquatable<Identity<T>>
{
private const string IdentityComponentDivider = ".";
public override bool Equals(object obj)
{
if (ReferenceEquals(this, obj)) return true;
if (ReferenceEquals(null, obj)) return false;
if (GetType() != obj.GetType()) return false;
var other = obj as Identity<T>;
return other != null && GetIdentityComponents().SequenceEqual(other.GetIdentityComponents());
}
public override string ToString()
{
var id = string.Empty;
foreach (var component in GetIdentityComponents())
{
if (string.IsNullOrEmpty(id))
id = component.ToString(); // first item, dont add a divider
else
id += IdentityComponentDivider + component;
}
return id;
}
protected abstract IEnumerable<object> GetIdentityComponents();
public override int GetHashCode()
{
return HashCodeHelper.CombineHashCodes(GetIdentityComponents());
}
public bool Equals(Identity<T> other)
{
return Equals(other as object);
}
}
is it possible?
Public String Get_Filed_By_Id(string table_Name,String Field_Name,string PK_val)
{
string strRes="";
using(mydbcontext db=new mydbcontext())
{
var x=db.table_Name.Where(p=>p.Id=PK_val).FirstOrDefault().Field_Name;
strRes=Convert.Tostring(x);
}
return strRes;
}
OR
var x=(from o in db.table_Name where o.Id=PK_val select o.Field_Name).FirstOrDefault();
Here, i'm passing Table_Name,Column_Name and the Condition value(PK_val) to Get the Column_Name from Table_Name within a Certain Condition(Id=Pk_val).
Is it possible??
Is it possible??
Yes, it is.
First, some helpers:
using System;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
namespace YourNamespace
{
internal static class DbHelpers
{
public static object GetColumnById(this object dbContext, string tableName, string columnName, object id)
{
var table = (IQueryable)dbContext.GetType().GetProperty(tableName).GetValue(dbContext, null);
var row = Expression.Parameter(table.ElementType, "row");
var filter = Expression.Lambda(Expression.Equal(Expression.Property(row, "Id"), Expression.Constant(id)), row);
var column = Expression.Property(row, columnName);
var selector = Expression.Lambda(column, row);
var query = Call(Where.MakeGenericMethod(row.Type), table, filter);
query = Call(Select.MakeGenericMethod(row.Type, column.Type), query, selector);
var value = Call(FirstOrDefault.MakeGenericMethod(column.Type), query);
return value;
}
private static readonly MethodInfo Select = GetGenericMethodDefinition<
Func<IQueryable<object>, Expression<Func<object, object>>, IQueryable<object>>>((source, selector) =>
Queryable.Select(source, selector));
private static readonly MethodInfo Where = GetGenericMethodDefinition<
Func<IQueryable<object>, Expression<Func<object, bool>>, object>>((source, predicate) =>
Queryable.Where(source, predicate));
private static readonly MethodInfo FirstOrDefault = GetGenericMethodDefinition<
Func<IQueryable<object>, object>>(source =>
Queryable.FirstOrDefault(source));
private static MethodInfo GetGenericMethodDefinition<TDelegate>(Expression<TDelegate> e)
{
return ((MethodCallExpression)e.Body).Method.GetGenericMethodDefinition();
}
private static object Call(MethodInfo method, params object[] parameters)
{
return method.Invoke(null, parameters);
}
}
}
and now your function:
public string Get_Field_By_Id(string table_Name, string field_Name, string PK_val)
{
using (var db = new mydbcontext())
return Convert.ToString(db.GetColumnById(table_Name, field_Name, PK_val));
}
It is not really possible with EntityFramework actually(as far as I know). If you only needed the field by its name, then you could have used #Den's proposed solution. But you want to specify the table name too as a parameter. So I suggest you to use standard Sql Connector api, and build the query string with the parameters you provide.
Check this link for usage of standard sql connector api.
I had this question too ,I know this is not exactly what you want and you need write more code but it's much cleaner than those you want to write.
Using repository pattern
For every table you should have a model class and Repository class.
Consider this code(this code from one of my project)
This is my comment table(this can be anything with or without navigation property)
public sealed class Comment
{
public string CommentText { get; set; }
public DateTime PostDate { get; set; }
public int PostId { get; set; }
public int? PageId { get; set; }
public Page Page { get; set; }
public User User { get; set; }
public string UserId { get; set; }
public int? ParentId { get; set; }
public Comment[] ChildComments { get; set; }
}
RepositoryComment
public sealed class CommentRepository : BaseRepository<Comment>
{
public CommentRepository(BabySitterContext context)
: base(context)
{
}
}
and a base class that you send your query with table name(here model) and field(you can extend clas for more functionality)
public class BaseRepository<T> where T : class
{
protected BabySitterContext Context;
private readonly PluralizationService _pluralizer = PluralizationService.CreateService(CultureInfo.GetCultureInfo("en"));
public BaseRepository(BabySitterContext context)
{
this.Context = context;
}
public bool Add(T t)
{
Context.Set<T>().Add(t);
Context.SaveChanges();
return true;
}
public bool Update(T t)
{
var entityName = GetEntityName<T>();
object originalItem;
var key = ((IObjectContextAdapter)Context).ObjectContext.CreateEntityKey(entityName, t);
if (((IObjectContextAdapter)Context).ObjectContext.TryGetObjectByKey(key, out originalItem))
{
((IObjectContextAdapter)Context).ObjectContext.ApplyCurrentValues(key.EntitySetName, t);
}
Context.SaveChanges();
return true;
}
public void Attach(T t)
{
if (t == null)
{
throw new ArgumentNullException("t");
}
Context.Set<T>().Attach(t);
Context.SaveChanges();
}
public void Remove(T t)
{
if (t == null)
{
throw new ArgumentNullException("t");
}
Context.Set<T>().Remove(t);
Context.SaveChanges();
}
public IEnumerable<T> Get(Expression<Func<T, bool>> filter = null, Func<IQueryable<T>, IOrderedQueryable<T>> orderBy = null, string includeProperties = "")
{
IQueryable<T> query = Context.Set<T>();
if (filter != null)
{
query = query.Where(filter.Expand());
}
foreach (var includeProperty in includeProperties.Split
(new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries))
{
query = query.Include(includeProperty);
}
if (orderBy != null)
{
return orderBy(query).ToList();
}
else
{
return query.ToList();
}
}
private string GetEntityName<TEntity>() where TEntity : class
{
return string.Format("{0}.{1}", ((IObjectContextAdapter)Context).ObjectContext.DefaultContainerName, _pluralizer.Pluralize(typeof(TEntity).Name));
}
public virtual IEnumerable<T> GetByBusinessKey(T entity)
{
return null;
}
}
For any other table just make model class and reposiotry then inherite from base class
Using code
var context = new BabySitterContext();
var _commentRepository = new CommentRepository(context);
var comment = _commentRepository.Get(x => x.PostId == id).FirstOrDefault();
No, but in this way
Public String Get_Filed_By_Id(string table_Name,String Field_Name,string PK_val)
{
string strRes="";
using(mydbcontext db=new mydbcontext())
{
var x=db.table_Name.Where(p=>p.Id=PK_val).Select(b=>b.Field_Name).FirstOrDefault();
strRes=Convert.Tostring(x);
}
return strRes;
}
I have the following C# code. Here the validations are kept outside the class to satisfy Open – Closed Principle. This is working fine. But the challenge is – the validations are not generic. It is specific to employee class (E.g DateOfBirthRuleForEmployee). How do I make the validations generic for all objects (DateOfBirthRuleForAnyObject).
Note: Make Generic <==> Make Type-Independent
Note: I have NameLengthRuleForEmployee validation also. New validation may come in future.
EDIT
Generic Method Example: Using “OfType” in LINQ
CODE
class Program
{
static void Main(string[] args)
{
Employee employee = new Employee();
employee.DateOfBirth = DateTime.Now;
employee.Name = "Lijo";
DateOfBirthRuleForEmployee dobRule = new
DateOfBirthRuleForEmployee();
NameLengthRuleForEmployee nameRule = new
NameLengthRuleForEmployee();
EmployeeManager employeeManager = new EmployeeManager();
employeeManager.AddRules(dobRule);
employeeManager.AddRules(nameRule);
bool result = employeeManager.validateEntity(employee);
Console.WriteLine(result);
Console.ReadLine();
}
}
public interface IEntity
{
}
public interface IRule<TEntity>
{
bool IsValid(TEntity entity);
}
public class DateOfBirthRuleForEmployee : IRule<Employee>
{
public bool IsValid(Employee entity)
{
return (entity.DateOfBirth.Year <= 1975);
}
}
public class NameLengthRuleForEmployee : IRule<Employee>
{
public bool IsValid(Employee employee)
{
return (employee.Name.Length < 5);
}
}
public class Employee : IEntity
{
private DateTime dateOfBirth;
private string name;
public DateTime DateOfBirth
{
get
{
return dateOfBirth;
}
set
{
dateOfBirth = value;
}
}
public string Name
{
get
{
return name;
}
set
{
name = value;
}
}
}
public class EmployeeManager
{
RulesEngine<Employee> engine = new RulesEngine<Employee>();
public void AddRules(IRule<Employee> rule)
{
engine.AddRules(rule);
//engine.AddRules(new NameLengthRuleForEmployee());
}
public bool validateEntity(Employee employee)
{
List<IRule<Employee>> rulesList = engine.GetRulesList();
//No need for type checking. Overcame Invariance problem
bool status = true;
foreach (IRule<Employee> theRule in rulesList)
{
if (!theRule.IsValid(employee))
{
status = false;
break;
}
}
return status;
}
}
public class RulesEngine<TEntity> where TEntity : IEntity
{
private List<IRule<TEntity>> ruleList = new
List<IRule<TEntity>>();
public void AddRules(IRule<TEntity> rule)
{
//invariance is the key term
ruleList.Add(rule);
}
public List<IRule<TEntity>> GetRulesList()
{
return ruleList;
}
}
The challange is for your rules to know which property of what type to validate. You can either provide this by implementing an interface that provides just that as suggested by SLaks or by quessing it dynamically or by providing a concrete rule class with a bit more information on how to access the given property, e.g.:
class NameRule<T> : IRule<T>
{
private Func<T, string> _nameAccessor;
public NameRule(Func<T, string> nameAccessor)
{
_nameAccessor = nameAccessor;
}
public bool IsValid(T instance)
{
return _nameAccessor(instance).Length > 10;
}
}
this ofcourse can be used in the following way:
NameRule<Employee> employeeNameRule = new NameRule<Employee>(x => x.name);
employeeManager.addRule(employeeNameRule);