Search Results

Search found 41 results on 2 pages for 'referenceequals'.

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

Page 1/2 | 1 2  | Next Page >

  • !(ReferenceEquals()) vs != in Entity Framework 4

    - by Eric J.
    Unless a class specifically overrides the behavior defined for Object, ReferenceEquals and == do the same thing... compare references. In property setters, I have commonly used the pattern private MyType myProperty; public MyType MyProperty { set { if (myProperty != value) { myProperty = value; // Do stuff like NotifyPropertyChanged } } } However, in code generated by Entity Framework, the if statement is replaced by if (!ReferenceEquals(myProperty, value)) Using ReferenceEquals is more explicit (as I guess not all C# programmers know that == does the same thing if not overridden). Is there any difference that's escaping me between the two if-variants? Are they perhaps accounting for the possibility that POCO designers may have overridden ==? In short, if I have not overridden ==, am I save using != instead of ReferencEquals()?

    Read the article

  • Entity Framework 4: C# !(ReferenceEquals()) vs !=

    - by Eric J.
    Unless a class specifically overrides the behavior defined for Object, ReferenceEquals and == do the same thing... compare references. In property setters, I have commonly used the pattern private MyType myProperty; public MyType MyProperty { set { if (myProperty != value) { myProperty = value; // Do stuff like NotifyPropertyChanged } } } However, in code generated by Entity Framework, the if statement is replaced by if (!ReferenceEquals(myProperty, value)) Using ReferenceEquals is more explicit (as I guess not all C# programmers know that == does the same thing if not overridden). Is there any difference that's escaping me between the two if-variants? Are they perhaps accounting for the possibility that POCO designers may have overridden ==? In short, if I have not overridden ==, am I save using != instead of ReferencEquals()?

    Read the article

  • How to use Object.GetHashCode() on a type that overrides GetHashCode()

    - by Jimmy
    Hi, I have a class A that implements IEquatable<, using its fields (say, A.b and A.c) for implementing/overriding Equals() and overriding GetHashCode(), and everything works fine, 99% of the time. Class A is part of a hierarchy (class B, C) that all inherit from interface D; they can all be stored together in a dictionary Dictionary, thus it's convenient when they all carry their own default Equals()/GetHashCode(). However, while constructing A I sometime need to do some work to get the values for A.b and A.c; while that's happening, I want to store a reference to the instance that's being built. In that case, I don't want to use the default Equals()/GetHashCode() overrides provided by A. Thus, I was thinking of implementing a ReferenceEqualityComparer, that's meant to force the use of Object's Equals()/GetHashCode(): private class ReferenceEqualityComparer<T> : IEqualityComparer<T> { #region IEqualityComparer<T> Members public bool Equals(T x, T y) { return System.Object.ReferenceEquals(x, y); } public int GetHashCode(T obj) { // what goes here? I want to do something like System.Object.GetHashCode(obj); } #endregion } The question is, since A overrides Object.GetHashCode(), how can I (outside of A) call Object.GetHashCode() for an instance of A? One way of course would be for A to not implement IEquatable< and always supply an IEqualityComparer< to any dictionary that I create, but I'm hoping for a different answer. Thanks

    Read the article

  • String interning?

    - by rkrauter
    The second ReferenceEquals call returns false. Why isn't the string in s4 interned? string s1 = "tom"; string s2 = "tom"; Console.Write(object.ReferenceEquals(s2, s1)); //true string s3 = "tom"; string s4 = "to"; s4 += "m"; Console.Write(object.ReferenceEquals(s3, s4)); //false

    Read the article

  • LINQ – SequenceEqual() method

    - by nmarun
    I have been looking at LINQ extension methods and have blogged about what I learned from them in my blog space. Next in line is the SequenceEqual() method. Here’s the description about this method: “Determines whether two sequences are equal by comparing the elements by using the default equality comparer for their type.” Let’s play with some code: 1: int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 }; 2: // int[] numbersCopy = numbers; 3: int[] numbersCopy = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 }; 4:  5: Console.WriteLine(numbers.SequenceEqual(numbersCopy)); This gives an output of ‘True’ – basically compares each of the elements in the two arrays and returns true in this case. The result is same even if you uncomment line 2 and comment line 3 (I didn’t need to say that now did I?). So then what happens for custom types? For this, I created a Product class with the following definition: 1: class Product 2: { 3: public int ProductId { get; set; } 4: public string Name { get; set; } 5: public string Category { get; set; } 6: public DateTime MfgDate { get; set; } 7: public Status Status { get; set; } 8: } 9:  10: public enum Status 11: { 12: Active = 1, 13: InActive = 2, 14: OffShelf = 3, 15: } In my calling code, I’m just adding a few product items: 1: private static List<Product> GetProducts() 2: { 3: return new List<Product> 4: { 5: new Product 6: { 7: ProductId = 1, 8: Name = "Laptop", 9: Category = "Computer", 10: MfgDate = new DateTime(2003, 4, 3), 11: Status = Status.Active, 12: }, 13: new Product 14: { 15: ProductId = 2, 16: Name = "Compact Disc", 17: Category = "Water Sport", 18: MfgDate = new DateTime(2009, 12, 3), 19: Status = Status.InActive, 20: }, 21: new Product 22: { 23: ProductId = 3, 24: Name = "Floppy", 25: Category = "Computer", 26: MfgDate = new DateTime(1993, 3, 7), 27: Status = Status.OffShelf, 28: }, 29: }; 30: } Now for the actual check: 1: List<Product> products1 = GetProducts(); 2: List<Product> products2 = GetProducts(); 3:  4: Console.WriteLine(products1.SequenceEqual(products2)); This one returns ‘False’ and the reason is simple – this one checks for reference equality and the products in the both the lists get different ‘memory addresses’ (sounds like I’m talking in ‘C’). In order to modify this behavior and return a ‘True’ result, we need to modify the Product class as follows: 1: class Product : IEquatable<Product> 2: { 3: public int ProductId { get; set; } 4: public string Name { get; set; } 5: public string Category { get; set; } 6: public DateTime MfgDate { get; set; } 7: public Status Status { get; set; } 8:  9: public override bool Equals(object obj) 10: { 11: return Equals(obj as Product); 12: } 13:  14: public bool Equals(Product other) 15: { 16: //Check whether the compared object is null. 17: if (ReferenceEquals(other, null)) return false; 18:  19: //Check whether the compared object references the same data. 20: if (ReferenceEquals(this, other)) return true; 21:  22: //Check whether the products' properties are equal. 23: return ProductId.Equals(other.ProductId) 24: && Name.Equals(other.Name) 25: && Category.Equals(other.Category) 26: && MfgDate.Equals(other.MfgDate) 27: && Status.Equals(other.Status); 28: } 29:  30: // If Equals() returns true for a pair of objects 31: // then GetHashCode() must return the same value for these objects. 32: // read why in the following articles: 33: // http://geekswithblogs.net/akraus1/archive/2010/02/28/138234.aspx 34: // http://stackoverflow.com/questions/371328/why-is-it-important-to-override-gethashcode-when-equals-method-is-overriden-in-c 35: public override int GetHashCode() 36: { 37: //Get hash code for the ProductId field. 38: int hashProductId = ProductId.GetHashCode(); 39:  40: //Get hash code for the Name field if it is not null. 41: int hashName = Name == null ? 0 : Name.GetHashCode(); 42:  43: //Get hash code for the ProductId field. 44: int hashCategory = Category.GetHashCode(); 45:  46: //Get hash code for the ProductId field. 47: int hashMfgDate = MfgDate.GetHashCode(); 48:  49: //Get hash code for the ProductId field. 50: int hashStatus = Status.GetHashCode(); 51: //Calculate the hash code for the product. 52: return hashProductId ^ hashName ^ hashCategory & hashMfgDate & hashStatus; 53: } 54:  55: public static bool operator ==(Product a, Product b) 56: { 57: // Enable a == b for null references to return the right value 58: if (ReferenceEquals(a, b)) 59: { 60: return true; 61: } 62: // If one is null and the other not. Remember a==null will lead to Stackoverflow! 63: if (ReferenceEquals(a, null)) 64: { 65: return false; 66: } 67: return a.Equals((object)b); 68: } 69:  70: public static bool operator !=(Product a, Product b) 71: { 72: return !(a == b); 73: } 74: } Now THAT kinda looks overwhelming. But lets take one simple step at a time. Ok first thing you’ve noticed is that the class implements IEquatable<Product> interface – the key step towards achieving our goal. This interface provides us with an ‘Equals’ method to perform the test for equality with another Product object, in this case. This method is called in the following situations: when you do a ProductInstance.Equals(AnotherProductInstance) and when you perform actions like Contains<T>, IndexOf() or Remove() on your collection Coming to the Equals method defined line 14 onwards. The two ‘if’ blocks check for null and referential equality using the ReferenceEquals() method defined in the Object class. Line 23 is where I’m doing the actual check on the properties of the Product instances. This is what returns the ‘True’ for us when we run the application. I have also overridden the Object.Equals() method which calls the Equals() method of the interface. One thing to remember is that anytime you override the Equals() method, its’ a good practice to override the GetHashCode() method and overload the ‘==’ and the ‘!=’ operators. For detailed information on this, please read this and this. Since we’ve overloaded the operators as well, we get ‘True’ when we do actions like: 1: Console.WriteLine(products1.Contains(products2[0])); 2: Console.WriteLine(products1[0] == products2[0]); This completes the full circle on the SequenceEqual() method. See the code used in the article here.

    Read the article

  • C# HashSet<T>

    - by Ben Griswold
    I hadn’t done much (read: anything) with the C# generic HashSet until I recently needed to produce a distinct collection.  As it turns out, HashSet<T> was the perfect tool. As the following snippet demonstrates, this collection type offers a lot: // Using HashSet<T>: // http://www.albahari.com/nutshell/ch07.aspx var letters = new HashSet<char>("the quick brown fox");   Console.WriteLine(letters.Contains('t')); // true Console.WriteLine(letters.Contains('j')); // false   foreach (char c in letters) Console.Write(c); // the quickbrownfx Console.WriteLine();   letters = new HashSet<char>("the quick brown fox"); letters.IntersectWith("aeiou"); foreach (char c in letters) Console.Write(c); // euio Console.WriteLine();   letters = new HashSet<char>("the quick brown fox"); letters.ExceptWith("aeiou"); foreach (char c in letters) Console.Write(c); // th qckbrwnfx Console.WriteLine();   letters = new HashSet<char>("the quick brown fox"); letters.SymmetricExceptWith("the lazy brown fox"); foreach (char c in letters) Console.Write(c); // quicklazy Console.WriteLine(); The MSDN documentation is a bit light on HashSet<T> documentation but if you search hard enough you can find some interesting information and benchmarks. But back to that distinct list I needed… // MSDN Add // http://msdn.microsoft.com/en-us/library/bb353005.aspx var employeeA = new Employee {Id = 1, Name = "Employee A"}; var employeeB = new Employee {Id = 2, Name = "Employee B"}; var employeeC = new Employee {Id = 3, Name = "Employee C"}; var employeeD = new Employee {Id = 4, Name = "Employee D"};   var naughty = new List<Employee> {employeeA}; var nice = new List<Employee> {employeeB, employeeC};   var employees = new HashSet<Employee>(); naughty.ForEach(x => employees.Add(x)); nice.ForEach(x => employees.Add(x));   foreach (Employee e in employees) Console.WriteLine(e); // Returns Employee A Employee B Employee C The Add Method returns true on success and, you guessed it, false if the item couldn’t be added to the collection.  I’m using the Linq ForEach syntax to add all valid items to the employees HashSet.  It works really great.  This is just a rough sample, but you may have noticed I’m using Employee, a reference type.  Most samples demonstrate the power of the HashSet with a collection of integers which is kind of cheating.  With value types you don’t have to worry about defining your own equality members.  With reference types, you do. internal class Employee {     public int Id { get; set; }     public string Name { get; set; }       public override string ToString()     {         return Name;     }          public bool Equals(Employee other)     {         if (ReferenceEquals(null, other)) return false;         if (ReferenceEquals(this, other)) return true;         return other.Id == Id;     }       public override bool Equals(object obj)     {         if (ReferenceEquals(null, obj)) return false;         if (ReferenceEquals(this, obj)) return true;         if (obj.GetType() != typeof (Employee)) return false;         return Equals((Employee) obj);     }       public override int GetHashCode()     {         return Id;     }       public static bool operator ==(Employee left, Employee right)     {         return Equals(left, right);     }       public static bool operator !=(Employee left, Employee right)     {         return !Equals(left, right);     } } Fortunately, with Resharper, it’s a snap. Click on the class name, ALT+INS and then follow with the handy dialogues. That’s it. Try out the HashSet<T>. It’s good stuff.

    Read the article

  • How to get distinct values from the List&lt;T&gt; with LINQ

    - by Vincent Maverick Durano
    Recently I was working with data from a generic List<T> and one of my objectives is to get the distinct values that is found in the List. Consider that we have this simple class that holds the following properties: public class Product { public string Make { get; set; } public string Model { get; set; } }   Now in the page code behind we will create a list of product by doing the following: private List<Product> GetProducts() { List<Product> products = new List<Product>(); Product p = new Product(); p.Make = "Samsung"; p.Model = "Galaxy S 1"; products.Add(p); p = new Product(); p.Make = "Samsung"; p.Model = "Galaxy S 2"; products.Add(p); p = new Product(); p.Make = "Samsung"; p.Model = "Galaxy Note"; products.Add(p); p = new Product(); p.Make = "Apple"; p.Model = "iPhone 4"; products.Add(p); p = new Product(); p.Make = "Apple"; p.Model = "iPhone 4s"; products.Add(p); p = new Product(); p.Make = "HTC"; p.Model = "Sensation"; products.Add(p); p = new Product(); p.Make = "HTC"; p.Model = "Desire"; products.Add(p); p = new Product(); p.Make = "Nokia"; p.Model = "Some Model"; products.Add(p); p = new Product(); p.Make = "Nokia"; p.Model = "Some Model"; products.Add(p); p = new Product(); p.Make = "Sony Ericsson"; p.Model = "800i"; products.Add(p); p = new Product(); p.Make = "Sony Ericsson"; p.Model = "800i"; products.Add(p); return products; }   And then let’s bind the products to the GridView. protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { Gridview1.DataSource = GetProducts(); Gridview1.DataBind(); } }   Running the code will display something like this in the page: Now what I want is to get the distinct row values from the list. So what I did is to use the LINQ Distinct operator and unfortunately it doesn't work. In order for it work is you must use the overload method of the Distinct operator for you to get the desired results. So I’ve added this IEqualityComparer<T> class to compare values: class ProductComparer : IEqualityComparer<Product> { public bool Equals(Product x, Product y) { if (Object.ReferenceEquals(x, y)) return true; if (Object.ReferenceEquals(x, null) || Object.ReferenceEquals(y, null)) return false; return x.Make == y.Make && x.Model == y.Model; } public int GetHashCode(Product product) { if (Object.ReferenceEquals(product, null)) return 0; int hashProductName = product.Make == null ? 0 : product.Make.GetHashCode(); int hashProductCode = product.Model.GetHashCode(); return hashProductName ^ hashProductCode; } }   After that you can then bind the GridView like this: protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { Gridview1.DataSource = GetProducts().Distinct(new ProductComparer()); Gridview1.DataBind(); } }   Running the page will give you the desired output below: As you notice, it now eliminates the duplicate rows in the GridView. Now what if we only want to get the distinct values for a certain field. For example I want to get the distinct “Make” values such as Samsung, Apple, HTC, Nokia and Sony Ericsson and populate them to a DropDownList control for filtering purposes. I was hoping the the Distinct operator has an overload that can compare values based on the property value like (GetProducts().Distinct(o => o.PropertyToCompare). But unfortunately it doesn’t provide that overload so what I did as a workaround is to use the GroupBy,Select and First LINQ query operators to achieve what I want. Here’s the code to get the distinct values of a certain field. protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { DropDownList1.DataSource = GetProducts().GroupBy(o => o.Make).Select(o => o.First()); DropDownList1.DataTextField = "Make"; DropDownList1.DataValueField = "Model"; DropDownList1.DataBind(); } } Running the code will display the following output below:   That’s it! I hope someone find this post useful!

    Read the article

  • equality on the sender of an event

    - by Berryl
    I have an interface for a UI widget, two of which are attributes of a presenter. public IMatrixWidget NonProjectActivityMatrix { set { // validate the incoming value and set the field _nonProjectActivityMatrix = value; .... // configure & load non-project activities } public IMatrixWidget ProjectActivityMatrix { set { // validate the incoming value and set the field _projectActivityMatrix = value; .... // configure & load project activities } The widget has an event that both presenter objects subscribe to, and so there is an event handler in the presenter like so: public void OnActivityEntry(object sender, EntryChangedEventArgs e) { // calculate newTotal here .... if (ReferenceEquals(sender, _nonProjectActivityMatrix)) { _nonProjectActivityMatrix.UpdateTotalHours(feedback.ActivityTotal); } else if (ReferenceEquals(sender, _projectActivityMatrix)) { _projectActivityMatrix.UpdateTotalHours(feedback.ActivityTotal); } else { // ERROR - we should never be here } } The problem is that the ReferenceEquals on the sender fails, even though it is the implemented widget that is the sender - the same implemented widget that was set to the presenter attribute! Can anyone spot what the problem / fix is? Cheers, Berryl I didn't know you could edit nicely. Cool. Here is the event raising code: void OnGridViewNumericUpDownEditingControl_ValueChanged(object sender, EventArgs e) { // omitted to save sapce if (EntryChanged == null) return; var args = new EntryChangedEventArgs(activityID, dayID, Convert.ToDouble(amount)); EntryChanged(this, args); } Here is the debugger dump of the presenter attribute, sans namespace info: ?_nonProjectActivityMatrix {WinPresentation.Widgets.MatrixWidgetDgv} [WinPresentation.Widgets.MatrixWidgetDgv]: {WinPresentation.Widgets.MatrixWidgetDgv} Here is the debugger dump of the sender: ?sender {WinPresentation.Widgets.MatrixWidgetDgv} base {Core.GUI.Widgets.Lookup.MatrixWidgetBase<Core.GUI.Widgets.Lookup.DynamicDisplayDto>}: {WinPresentation.Widgets.MatrixWidgetDgv} _configuration: {Domain.Presentation.Timesheet.Matrix.WeeklyMatrixConfiguration} _wrappedWidget: {Win.Widgets.DataGridViewDynamicLookupWidget} AllowUserToAddRows: true ColumnCount: 11 Count: 4 EntryChanged: {Method = {Void OnActivityEntry(System.Object, Smack.ConstructionAdmin.Domain.Presentation.Timesheet.Matrix.EntryChangedEventArgs)}} SelectedCell: {DataGridViewNumericUpDownCell { ColumnIndex=3, RowIndex=3 }} SelectedCellValue: "0.00" SelectedColumn: {DataGridViewNumericUpDownColumn { Name=MONDAY, Index=3 }} SelectedItem: {'AdministrativeActivity: 130-04', , AdministrativeTime, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00, 0.00} Berryl

    Read the article

  • Lightcore IoC is returning the same instance when it should give a new one

    - by Anthony
    I have the following code using the lightcore IoC container. But it fails with "NUnit.Framework.AssertionException: Contained objects are equal" which indicates that the objects that should be transient, are not. Is this a bug in lightcore, or am I doing it wrong? [Test] public void JellybeanDispenserHasNewInstanceEachTimeWithDefault() { var builder = new ContainerBuilder(); builder.Register<IJellybeanDispenser, VanillaJellybeanDispenser>(); builder.Register<SweetVendingMachine>().ControlledBy<TransientLifecycle>(); builder.Register<SweetShop>(); builder.DefaultControlledBy<TransientLifecycle>(); IContainer container = builder.Build(); SweetShop sweetShop = container.Resolve<SweetShop>(); SweetShop sweetShop2 = container.Resolve<SweetShop>(); Assert.IsFalse(ReferenceEquals(sweetShop, sweetShop2), "Root objects are equal"); Assert.IsFalse(ReferenceEquals(sweetShop.SweetVendingMachine, sweetShop2.SweetVendingMachine), "Contained objects are equal"); Assert.IsFalse(ReferenceEquals(sweetShop.SweetVendingMachine.JellybeanDispenser, sweetShop2.SweetVendingMachine.JellybeanDispenser), "services are equal"); } PS: I would tag this question with "lightcore", but suddenly my reputation isn't good enough to make a new tag. Huh.

    Read the article

  • NHibernate MySQL Composite-Key

    - by LnDCobra
    I am trying to create a composite key that mimicks the set of PrimaryKeys in the built in MySQL.DB table. The Db primary key is as follows: Field | Type | Null | ---------------------------------- Host | char(60) | No | Db | char(64) | No | User | char(16) | No | This is my DataBasePrivilege.hbm.xml file <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="TGS.MySQL.DataBaseObjects" namespace="TGS.MySQL.DataBaseObjects"> <class name="TGS.MySQL.DataBaseObjects.DataBasePrivilege,TGS.MySQL.DataBaseObjects" table="db"> <composite-id name="CompositeKey" class="TGS.MySQL.DataBaseObjects.DataBasePrivilegePrimaryKey, TGS.MySQL.DataBaseObjects"> <key-property name="Host" column="Host" type="char" length="60" /> <key-property name="DataBase" column="Db" type="char" length="64" /> <key-property name="User" column="User" type="char" length="16" /> </composite-id> </class> </hibernate-mapping> The following are my 2 classes for my composite key: namespace TGS.MySQL.DataBaseObjects { public class DataBasePrivilege { public virtual DataBasePrivilegePrimaryKey CompositeKey { get; set; } } public class DataBasePrivilegePrimaryKey { public string Host { get; set; } public string DataBase { get; set; } public string User { get; set; } public override bool Equals(object obj) { if (ReferenceEquals(null, obj)) return false; if (ReferenceEquals(this, obj)) return true; if (obj.GetType() != typeof (DataBasePrivilegePrimaryKey)) return false; return Equals((DataBasePrivilegePrimaryKey) obj); } public bool Equals(DataBasePrivilegePrimaryKey other) { if (ReferenceEquals(null, other)) return false; if (ReferenceEquals(this, other)) return true; return Equals(other.Host, Host) && Equals(other.DataBase, DataBase) && Equals(other.User, User); } public override int GetHashCode() { unchecked { int result = (Host != null ? Host.GetHashCode() : 0); result = (result*397) ^ (DataBase != null ? DataBase.GetHashCode() : 0); result = (result*397) ^ (User != null ? User.GetHashCode() : 0); return result; } } } } And the following is the exception I am getting: Execute System.InvalidCastException: Unable to cast object of type 'System.Object[]' to type 'TGS.MySQL.DataBaseObjects.DataBasePrivilegePrimaryKey'. at (Object , GetterCallback ) at NHibernate.Bytecode.Lightweight.AccessOptimizer.GetPropertyValues(Object target) at NHibernate.Tuple.Component.PocoComponentTuplizer.GetPropertyValues(Object component) at NHibernate.Type.ComponentType.GetPropertyValues(Object component, EntityMode entityMode) at NHibernate.Type.ComponentType.GetHashCode(Object x, EntityMode entityMode) at NHibernate.Type.ComponentType.GetHashCode(Object x, EntityMode entityMode, ISessionFactoryImplementor factory) at NHibernate.Engine.EntityKey.GenerateHashCode() at NHibernate.Engine.EntityKey..ctor(Object identifier, String rootEntityName, String entityName, IType identifierType, Boolean batchLoadable, ISessionFactoryImplementor factory, EntityMode entityMode) at NHibernate.Engine.EntityKey..ctor(Object id, IEntityPersister persister, EntityMode entityMode) at NHibernate.Event.Default.DefaultLoadEventListener.OnLoad(LoadEvent event, LoadType loadType) at NHibernate.Impl.SessionImpl.FireLoad(LoadEvent event, LoadType loadType) at NHibernate.Impl.SessionImpl.Get(String entityName, Object id) at NHibernate.Impl.SessionImpl.Get(Type entityClass, Object id) at NHibernate.Impl.SessionImpl.Get[T](Object id) at TGS.MySQL.DataBase.DataProvider.GetDatabasePrivilegeByHostDbUser(String host, String db, String user) in C:\Documents and Settings\Michal\My Documents\Visual Studio 2008\Projects\TGS\TGS.MySQL.DataBase\DataProvider.cs:line 20 at TGS.UserAccountControl.UserAccountManager.GetDatabasePrivilegeByHostDbUser(String host, String db, String user) in C:\Documents and Settings\Michal\My Documents\Visual Studio 2008\Projects\TGS\TGS.UserAccountControl\UserAccountManager.cs:line 10 at TGS.UserAccountControlTest.UserAccountManagerTest.CanGetDataBasePrivilegeByHostDbUser() in C:\Documents and Settings\Michal\My Documents\Visual Studio 2008\Projects\TGS\TGS.UserAccountControlTest\UserAccountManagerTest.cs:line 12 I am new to NHibernate and any help would be appreciated. I just can't see where it is getting the object[] from? Is the composite key supposed to be object[]?

    Read the article

  • how to make condition to update table ?

    - by newBie
    hi..i want to make condition to update my table if there's already same data (in the same column) inserted in the table. im using If String.ReferenceEquals(hotel, hotel) = False Then insertDatabase() Else updateDatabase() End If this is the updateDatabase() code Dim sql2 As String = "update infoHotel set nameHotel = N" & FormatSqlParam(hotel) & _ ", knownAs1 = N" & FormatSqlParam(KnownAs(0)) & _ ", knownAs2 = N" & FormatSqlParam(KnownAs(1)) & _ ", knownAs3 = N" & FormatSqlParam(KnownAs(2)) & _ ", knownAs4 = N" & FormatSqlParam(KnownAs(3)) & _ " where hotel = " & hotel & ")" the function manage to go into updateDatabase() but has some error saying "Incorrect syntax near 'Oriental'." Oriental is the data inserted in the table. is it suitable to use ReferenceEquals? im using vb.net and sql database..tq

    Read the article

  • Resolving Circular References for Objects Implementing ISerializable

    - by Chris
    I'm writing my own IFormatter implementation and I cannot think of a way to resolve circular references between two types that both implement ISerializable. Here's the usual pattern: [Serializable] class Foo : ISerializable { private Bar m_bar; public Foo(Bar bar) { m_bar = bar; m_bar.Foo = this; } public Bar Bar { get { return m_bar; } } protected Foo(SerializationInfo info, StreamingContext context) { m_bar = (Bar)info.GetValue("1", typeof(Bar)); } public void GetObjectData(SerializationInfo info, StreamingContext context) { info.AddValue("1", m_bar); } } [Serializable] class Bar : ISerializable { private Foo m_foo; public Foo Foo { get { return m_foo; } set { m_foo = value; } } public Bar() { } protected Bar(SerializationInfo info, StreamingContext context) { m_foo = (Foo)info.GetValue("1", typeof(Foo)); } public void GetObjectData(SerializationInfo info, StreamingContext context) { info.AddValue("1", m_foo); } } I then do this: Bar b = new Bar(); Foo f = new Foo(b); bool equal = ReferenceEquals(b, b.Foo.Bar); // true // Serialise and deserialise b equal = ReferenceEquals(b, b.Foo.Bar); If I use an out-of-the-box BinaryFormatter to serialise and deserialise b, the above test for reference-equality returns true as one would expect. But I cannot conceive of a way to achieve this in my custom IFormatter. In a non-ISerializable situation I can simply revisit "pending" object fields using reflection once the target references have been resolved. But for objects implementing ISerializable it is not possible to inject new data using SerializationInfo. Can anyone point me in the right direction?

    Read the article

  • C# how to calculate hashcode from an object reference.

    - by Wayne
    Folks, here's a thorny problem for you! A part of the TickZoom system must collect instances of every type of object into a Dictionary< type. It is imperative that their equality and hash code be based on the instance of the object which means reference equality instead of value equality. The challenge is that some of the objects in the system have overridden Equals() and GetHashCode() for use as value equality and their internal values will change over time. That means that their Equals and GetHashCode are useless. How to solve this generically rather than intrusively? So far, We created a struct to wrap each object called ObjectHandle for hashing into the Dictionary. As you see below we implemented Equals() but the problem of how to calculate a hash code remains. public struct ObjectHandle : IEquatable<ObjectHandle>{ public object Object; public bool Equals(ObjectHandle other) { return object.ReferenceEquals(this.Object,other.Object); } } See? There is the method object.ReferenceEquals() which will compare reference equality without regard for any overridden Equals() implementation in the object. Now, how to calculate a matching GetHashCode() by only considering the reference without concern for any overridden GetHashCode() method? Ahh, I hope this give you an interesting puzzle. We're stuck over here. Sincerely, Wayne

    Read the article

  • Can't seem to get .Union to work (merging 2 array's together, exclude duplicates)

    - by D. Veloper
    I want to combine two array's, excluding duplicates. I am using a custom class: public class ArcContact : IEquatable<ArcContact> { public String Text; public Boolean Equals(ArcContact other) { if (Object.ReferenceEquals(other, null)) return false; if (Object.ReferenceEquals(this, other)) return true; return Text.Equals(other.Text); } public override Int32 GetHashCode() { return Text == null ? 0 : Text.GetHashCode(); } } I implemented and the needed IEquatable interface as mentioned in this msdn section. I only want to check the Text property of the ArcContact class and make sure an Array of ArcContact have an unique Text. Here I pasted the code that I use, as you can see I have method with two parameters, array's to combine and below that the code I got from the previous mentioned msdn section. internal static class ArcBizz { internal static ArcContact[] MergeDuplicateContacts(ArcContact[] contacts1, ArcContact[] contacts2) { return (ArcContact[])contacts1.Union(contacts2); } internal static IEnumerable<T> Union<T>(this IEnumerable<T> a, IEnumerable<T> b); } What am I doing wrong?

    Read the article

  • How to properly add .NET assemblies to Powershell session?

    - by amandion
    I have a .NET assembly (a dll) which is an API to backup software we use here. It contains some properties and methods I would like to take advantage of in my Powershell script(s). However, I am running into a lot of issues with first loading the assembly, then using any of the types once the assembly is loaded. The complete file path is: C:\rnd\CloudBerry.Backup.API.dll In Powershell I use: $dllpath = "C:\rnd\CloudBerry.Backup.API.dll" Add-Type -Path $dllpath I get the error below: Add-Type : Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information. At line:1 char:9 + Add-Type <<<< -Path $dllpath + CategoryInfo : NotSpecified: (:) [Add-Type], ReflectionTypeLoadException + FullyQualifiedErrorId : System.Reflection.ReflectionTypeLoadException,Microsoft.PowerShell.Commands.AddTypeComma ndAdd-Type : Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information. Using the same cmdlet on another .NET assembly, DotNetZip, which has examples of using the same functionality on the site also does not work for me. I eventually find that I am seemingly able to load the assembly using reflection: [System.Reflection.Assembly]::LoadFrom($dllpath) Although I don't understand the difference between the methods Load, LoadFrom, or LoadFile that last method seems to work. However, I still seem to be unable to create instances or use objects. Each time I try, I get errors that describe that Powershell is unable to find any of the public types. I know the classes are there: $asm = [System.Reflection.Assembly]::LoadFrom($dllpath) $cbbtypes = $asm.GetExportedTypes() $cbbtypes | Get-Member -Static ---- start of excerpt ---- TypeName: CloudBerryLab.Backup.API.BackupProvider Name MemberType Definition ---- ---------- ---------- PlanChanged Event System.EventHandler`1[CloudBerryLab.Backup.API.Utils.ChangedEventArgs] PlanChanged(Sy... PlanRemoved Event System.EventHandler`1[CloudBerryLab.Backup.API.Utils.PlanRemoveEventArgs] PlanRemoved... CalculateFolderSize Method static long CalculateFolderSize() Equals Method static bool Equals(System.Object objA, System.Object objB) GetAccounts Method static CloudBerryLab.Backup.API.Account[], CloudBerry.Backup.API, Version=1.0.0.1, Cu... GetBackupPlans Method static CloudBerryLab.Backup.API.BackupPlan[], CloudBerry.Backup.API, Version=1.0.0.1,... ReferenceEquals Method static bool ReferenceEquals(System.Object objA, System.Object objB) SetProfilePath Method static System.Void SetProfilePath(string profilePath) ----end of excerpt---- Trying to use static methods fail, I don't know why!!! [CloudBerryLab.Backup.API.BackupProvider]::GetAccounts() Unable to find type [CloudBerryLab.Backup.API.BackupProvider]: make sure that the assembly containing this type is load ed. At line:1 char:42 + [CloudBerryLab.Backup.API.BackupProvider] <<<< ::GetAccounts() + CategoryInfo : InvalidOperation: (CloudBerryLab.Backup.API.BackupProvider:String) [], RuntimeException + FullyQualifiedErrorId : TypeNotFound Any guidance appreciated!!

    Read the article

  • Entity Framework 4.0 and DDD patterns

    - by Voice
    Hi everybody I use EntityFramework as ORM and I have simple POCO Domain Model with two base classes that represent Value Object and Entity Object Patterns (Evans). These two patterns is all about equality of two objects, so I overrode Equals and GetHashCode methods. Here are these two classes: public abstract class EntityObject<T>{ protected T _ID = default(T); public T ID { get { return _ID; } protected set { _ID = value; } } public sealed override bool Equals(object obj) { EntityObject<T> compareTo = obj as EntityObject<T>; return (compareTo != null) && ((HasSameNonDefaultIdAs(compareTo) || (IsTransient && compareTo.IsTransient)) && HasSameBusinessSignatureAs(compareTo)); } public virtual void MakeTransient() { _ID = default(T); } public bool IsTransient { get { return _ID == null || _ID.Equals(default(T)); } } public override int GetHashCode() { if (default(T).Equals(_ID)) return 0; return _ID.GetHashCode(); } private bool HasSameBusinessSignatureAs(EntityObject<T> compareTo) { return ToString().Equals(compareTo.ToString()); } private bool HasSameNonDefaultIdAs(EntityObject<T> compareTo) { return (_ID != null && !_ID.Equals(default(T))) && (compareTo._ID != null && !compareTo._ID.Equals(default(T))) && _ID.Equals(compareTo._ID); } public override string ToString() { StringBuilder str = new StringBuilder(); str.Append(" Class: ").Append(GetType().FullName); if (!IsTransient) str.Append(" ID: " + _ID); return str.ToString(); } } public abstract class ValueObject<T, U> : IEquatable<T> where T : ValueObject<T, U> { private static List<PropertyInfo> Properties { get; set; } private static Func<ValueObject<T, U>, PropertyInfo, object[], object> _GetPropValue; static ValueObject() { Properties = new List<PropertyInfo>(); var propParam = Expression.Parameter(typeof(PropertyInfo), "propParam"); var target = Expression.Parameter(typeof(ValueObject<T, U>), "target"); var indexPar = Expression.Parameter(typeof(object[]), "indexPar"); var call = Expression.Call(propParam, typeof(PropertyInfo).GetMethod("GetValue", new[] { typeof(object), typeof(object[]) }), new[] { target, indexPar }); var lambda = Expression.Lambda<Func<ValueObject<T, U>, PropertyInfo, object[], object>>(call, target, propParam, indexPar); _GetPropValue = lambda.Compile(); } public U ID { get; protected set; } public override Boolean Equals(Object obj) { if (ReferenceEquals(null, obj)) return false; if (obj.GetType() != GetType()) return false; return Equals(obj as T); } public Boolean Equals(T other) { if (ReferenceEquals(null, other)) return false; if (ReferenceEquals(this, other)) return true; foreach (var property in Properties) { var oneValue = _GetPropValue(this, property, null); var otherValue = _GetPropValue(other, property, null); if (null == oneValue && null == otherValue) return false; if (false == oneValue.Equals(otherValue)) return false; } return true; } public override Int32 GetHashCode() { var hashCode = 36; foreach (var property in Properties) { var propertyValue = _GetPropValue(this, property, null); if (null == propertyValue) continue; hashCode = hashCode ^ propertyValue.GetHashCode(); } return hashCode; } public override String ToString() { var stringBuilder = new StringBuilder(); foreach (var property in Properties) { var propertyValue = _GetPropValue(this, property, null); if (null == propertyValue) continue; stringBuilder.Append(propertyValue.ToString()); } return stringBuilder.ToString(); } protected static void RegisterProperty(Expression<Func<T, Object>> expression) { MemberExpression memberExpression; if (ExpressionType.Convert == expression.Body.NodeType) { var body = (UnaryExpression)expression.Body; memberExpression = body.Operand as MemberExpression; } else memberExpression = expression.Body as MemberExpression; if (null == memberExpression) throw new InvalidOperationException("InvalidMemberExpression"); Properties.Add(memberExpression.Member as PropertyInfo); } } Everything was OK until I tried to delete some related objects (aggregate root object with two dependent objects which was marked for cascade deletion): I've got an exception "The relationship could not be changed because one or more of the foreign-key properties is non-nullable". I googled this and found http://blog.abodit.com/2010/05/the-relationship-could-not-be-changed-because-one-or-more-of-the-foreign-key-properties-is-non-nullable/ I changed GetHashCode to base.GetHashCode() and error disappeared. But now it breaks all my code: I can't override GetHashCode for my POCO objects = I can't override Equals = I can't implement Value Object and Entity Object patters for my POCO objects. So, I appreciate any solutions, workarounds here etc.

    Read the article

  • GetHashCode on null fields?

    - by Shimmy
    How do I deal with null fields in GetHashCode function? Module Module1 Sub Main() Dim c As New Contact Dim hash = c.GetHashCode End Sub Public Class Contact : Implements IEquatable(Of Contact) Public Name As String Public Address As String Public Overloads Function Equals(ByVal other As Contact) As Boolean _ Implements System.IEquatable(Of Contact).Equals Return Name = other.Name AndAlso Address = other.Address End Function Public Overrides Function Equals(ByVal obj As Object) As Boolean If ReferenceEquals(Me, obj) Then Return True If TypeOf obj Is Contact Then Return Equals(DirectCast(obj, Contact)) Else Return False End If End Function Public Overrides Function GetHashCode() As Integer Return Name.GetHashCode Xor Address.GetHashCode End Function End Class End Module

    Read the article

  • c# event fires windows form incorrectly

    - by MikeW
    I'm trying to understand what's happening here. I have a CheckedListBox which contains some ticked and some un-ticked items. I'm trying to find a way of determining the delta in the selection of controls. I've tried some cumbersome like this - but only works part of the time, I'm sure there's a more elegant solution. A maybe related problem is the myCheckBox_ItemCheck event fires on form load - before I have a chance to perform an ItemCheck. Here's what I have so far: void clbProgs_ItemCheck(object sender, ItemCheckEventArgs e) { // i know its awful System.Windows.Forms.CheckedListBox cb = (System.Windows.Forms.CheckedListBox)sender; string sCurrent = e.CurrentValue.ToString(); int sIndex = e.Index; AbstractLink lk = (AbstractLink)cb.Items[sIndex]; List<ILink> _links = clbProgs.DataSource as List<ILink>; foreach (AbstractLink lkCurrent in _links) { if (!lkCurrent.IsActive) { if (!_groupValues.ContainsKey(lkCurrent.Linkid)) { _groupValues.Add(lkCurrent.Linkid, lkCurrent); } } } if (_groupValues.ContainsKey(lk.Linkid)) { AbstractLink lkDirty = (AbstractLink)lk.Clone(); CheckState newValue = (CheckState)e.NewValue; if (newValue == CheckState.Checked) { lkDirty.IsActive = true; } else if (newValue == CheckState.Unchecked) { lkDirty.IsActive = false; } if (_dirtyGroups.ContainsKey(lk.Linkid)) { _dirtyGroups[lk.Linkid] = lkDirty; } else { CheckState oldValue = (CheckState)e.NewValue; if (oldValue == CheckState.Checked) { lkDirty.IsActive = true; } else if (oldValue == CheckState.Unchecked) { lkDirty.IsActive = false; } _dirtyGroups.Add(lk.Linkid, lk); } } else { if (!lk.IsActive) { _dirtyGroups.Add(lk.Linkid, lk); } else { _groupValues.Add(lk.Linkid, lk); } } } Then onclick of a save button - I check whats changed before sending to database: private void btSave_Click(object sender, EventArgs e) { List<AbstractLink> originalList = new List<AbstractLink>(_groupValues.Values); List<AbstractLink> changedList = new List<AbstractLink>(_dirtyGroups.Values); IEnumerable<AbstractLink> dupes = originalList.ToArray<AbstractLink>().Intersect(changedList.ToArray<AbstractLink>()); foreach (ILink t in dupes) { MessageBox.Show("Changed"); } if (dupes.Count() == 0) { MessageBox.Show("No Change"); } } For further info. The definition of type AbstractLink uses: public bool Equals(ILink other) { if (Object.ReferenceEquals(other, null)) return false; if (Object.ReferenceEquals(this, other)) return true; return IsActive.Equals(other.IsActive) && Linkid.Equals(other.Linkid); }

    Read the article

  • NHibernate IUserType convert nullable DateTime to DB not-null value

    - by barakbbn
    I have legacy DB that store dates that means no-date as 9999-21-31, The column Till_Date is of type DateTime not-null="true". in the application i want to build persisted class that represent no-date as null, So i used nullable DateTime in C# //public DateTime? TillDate {get; set; } I created IUserType that knows to convert the entity null value to DB 9999-12-31 but it seems that NHibernate doesn't call SafeNullGet, SafeNullSet on my IUserType when the entity value is null, and report a null is used for not-null column. I tried to by-pass it by mapping the column as not-null="false" (changed only the mapping file, not the DB) but it still didn't help, only now it tries to insert the null value to the DB and get ADOException. Any knowledge if NHibernate doesn't support IUseType that convert null to not-null values? Thanks //Implementation public class NullableDateTimeToNotNullUserType : IUserType { private static readonly DateTime MaxDate = new DateTime(9999, 12, 31); public new bool Equals(object x, object y) { //This didn't work as well if (ReferenceEquals(x, y)) return true; //if(x == null && y == null) return false; if (x == null || y == null) return false; return x.Equals(y); } public int GetHashCode(object x) { return x == null ? 0 : x.GetHashCode(); } public object NullSafeGet(IDataReader rs, string[] names, object owner) { var value = rs.GetDateTime(rs.GetOrdinal(names[0])); return (value == MaxDate)? null : value; } public void NullSafeSet(IDbCommand cmd, object value, int index) { var dateValue = (DateTime?)value; var dbValue = (dateValue.HasValue) ? dateValue.Value : MaxDate; ((IDataParameter)cmd.Parameters[index]).Value = dbValue; } public object DeepCopy(object value) { return value; } public object Replace(object original, object target, object owner) { return original; } public object Assemble(object cached, object owner) { return cached; } public object Disassemble(object value) { return value; } public SqlType[] SqlTypes { get { return new[] { NHibernateUtil.DateTime.SqlType }; } } public Type ReturnedType { get { return typeof(DateTime?); } } public bool IsMutable { get { return false; } } } } //Final Implementation with fixes. make the column mapping in hbm.xml not-null="false" public class NullableDateTimeToNotNullUserType : IUserType { private static readonly DateTime MaxDate = new DateTime(9999, 12, 31); public new bool Equals(object x, object y) { //This didn't work as well if (ReferenceEquals(x, y)) return true; //if(x == null && y == null) return false; if (x == null || y == null) return false; return x.Equals(y); } public int GetHashCode(object x) { return x == null ? 0 : x.GetHashCode(); } public object NullSafeGet(IDataReader rs, string[] names, object owner) { var value = NHibernateUtil.Date.NullSafeGet(rs, names[0]); return (value == MaxDate)? default(DateTime?) : value; } public void NullSafeSet(IDbCommand cmd, object value, int index) { var dateValue = (DateTime?)value; var dbValue = (dateValue.HasValue) ? dateValue.Value : MaxDate; NHibernateUtil.Date.NullSafeSet(cmd, valueToSet, index); } public object DeepCopy(object value) { return value; } public object Replace(object original, object target, object owner) { return original; } public object Assemble(object cached, object owner) { return cached; } public object Disassemble(object value) { return value; } public SqlType[] SqlTypes { get { return new[] { NHibernateUtil.DateTime.SqlType }; } } public Type ReturnedType { get { return typeof(DateTime?); } } public bool IsMutable { get { return false; } } } }

    Read the article

  • Fluent NHibernate: mapping complex many-to-many (with additional columns) and setting fetch

    - by HackedByChinese
    I need a Fluent NHibernate mapping that will fulfill the following (if nothing else, I'll also take the appropriate NHibernate XML mapping and reverse engineer it). DETAILS I have a many-to-many relationship between two entities: Parent and Child. That is accomplished by an additional table to store the identities of the Parent and Child. However, I also need to define two additional columns on that mapping that provide more information about the relationship. This is roughly how I've defined my types, at least the relevant parts (where Entity is some base type that provides an Id property and checks for equivalence based on that Id): public class Parent : Entity { public virtual IList<ParentChildRelationship> Children { get; protected set; } public virtual void AddChildRelationship(Child child, int customerId) { var relationship = new ParentChildRelationship { CustomerId = customerId, Parent = this, Child = child }; if (Children == null) Children = new List<ParentChildRelationship>(); if (Children.Contains(relationship)) return; relationship.Sequence = Children.Count; Children.Add(relationship); } } public class Child : Entity { // child doesn't care about its relationships } public class ParentChildRelationship { public int CustomerId { get; set; } public Parent Parent { get; set; } public Child Child { get; set; } public int Sequence { get; set; } public override bool Equals(object obj) { if (ReferenceEquals(null, obj)) return false; if (ReferenceEquals(this, obj)) return true; var other = obj as ParentChildRelationship; if (return other == null) return false; return (CustomerId == other.CustomerId && Parent == other.Parent && Child == other.Child); } public override int GetHashCode() { unchecked { int result = CustomerId; result = Parent == null ? 0 : (result*397) ^ Parent.GetHashCode(); result = Child == null ? 0 : (result*397) ^ Child.GetHashCode(); return result; } } } The tables in the database look approximately like (assume primary/foreign keys and forgive syntax): create table Parent ( id int identity(1,1) not null ) create table Child ( id int identity(1,1) not null ) create table ParentChildRelationship ( customerId int not null, parent_id int not null, child_id int not null, sequence int not null ) I'm OK with Parent.Children being a lazy loaded property. However, the ParentChildRelationship should eager load ParentChildRelationship.Child. Furthermore, I want to use a Join when I eager load. The SQL, when accessing Parent.Children, NHibernate should generate an equivalent query to: SELECT * FROM ParentChildRelationship rel LEFT OUTER JOIN Child ch ON rel.child_id = ch.id WHERE parent_id = ? OK, so to do that I have mappings that look like this: ParentMap : ClassMap<Parent> { public ParentMap() { Table("Parent"); Id(c => c.Id).GeneratedBy.Identity(); HasMany(c => c.Children).KeyColumn("parent_id"); } } ChildMap : ClassMap<Child> { public ChildMap() { Table("Child"); Id(c => c.Id).GeneratedBy.Identity(); } } ParentChildRelationshipMap : ClassMap<ParentChildRelationship> { public ParentChildRelationshipMap() { Table("ParentChildRelationship"); CompositeId() .KeyProperty(c => c.CustomerId, "customerId") .KeyReference(c => c.Parent, "parent_id") .KeyReference(c => c.Child, "child_id"); Map(c => c.Sequence).Not.Nullable(); } } So, in my test if i try to get myParentRepo.Get(1).Children, it does in fact get me all the relationships and, as I access them from the relationship, the Child objects (for example, I can grab them all by doing parent.Children.Select(r => r.Child).ToList()). However, the SQL that NHibernate is generating is inefficient. When I access parent.Children, NHIbernate does a SELECT * FROM ParentChildRelationship WHERE parent_id = 1 and then a SELECT * FROM Child WHERE id = ? for each child in each relationship. I understand why NHibernate is doing this, but I can't figure out how to set up the mapping to make NHibernate query the way I mentioned above.

    Read the article

  • linq Except and custom IEqualityComparer

    - by Joe
    I'm trying to implement a custom comparer on two lists of strings and use the .Except() linq method to get those that aren't one one of the lists. The reason I'm doing a custom comparer is because I need to do a "fuzzy" compare, i.e. one string on one list could be embedded inside a string on the other list. I've made the following comparer ` public class ItemFuzzyMatchComparer : IEqualityComparer { bool IEqualityComparer<string>.Equals(string x, string y) { return (x.Contains(y) || y.Contains(x)); } int IEqualityComparer<string>.GetHashCode(string obj) { if (Object.ReferenceEquals(obj, null)) return 0; return obj.GetHashCode(); } } ` When I debug, the only breakpoint that hits is in the GetHashCode() method. The Equals() never gets touched. Any ideas?

    Read the article

  • How do you override operator == when using interfaces instead of actual types?

    - by RickL
    I have some code like this: How should I implement the operator == so that it will be called when the variables are of interface IMyClass? public class MyClass : IMyClass { public static bool operator ==(MyClass a, MyClass b) { if (ReferenceEquals(a, b)) return true; if ((Object)a == null || (Object)b == null) return false; return false; } public static bool operator !=(MyClass a, MyClass b) { return !(a == b); } } class Program { static void Main(string[] args) { IMyClass m1 = new MyClass(); IMyClass m2 = new MyClass(); MyClass m3 = new MyClass(); MyClass m4 = new MyClass(); Console.WriteLine(m1 == m2); // does not go into custom == function. why not? Console.WriteLine(m3 == m4); // DOES go into custom == function } }

    Read the article

  • Why does String.Equals(Object obj) check to see if this == null?

    - by m-y
    // Determines whether two strings match. [ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)] public override bool Equals(Object obj) { //this is necessary to guard against reverse-pinvokes and //other callers who do not use the callvirt instruction if (this == null) throw new NullReferenceException(); String str = obj as String; if (str == null) return false; if (Object.ReferenceEquals(this, obj)) return true; return EqualsHelper(this, str); } The part I don't understand is the fact that it is checking for the current instance, this, against null. The comment is a bit confusing, so I was wondering what does that comment actually mean? Can anyone give an example of how this could break if that check was not there, and does this mean that I should also place that check in my classes?

    Read the article

  • NHibernate Pitfalls: Custom Types and Detecting Changes

    - by Ricardo Peres
    This is part of a series of posts about NHibernate Pitfalls. See the entire collection here. NHibernate supports the declaration of properties of user-defined types, that is, not entities, collections or primitive types. These are used for mapping a database columns, of any type, into a different type, which may not even be an entity; think, for example, of a custom user type that converts a BLOB column into an Image. User types must implement interface NHibernate.UserTypes.IUserType. This interface specifies an Equals method that is used for comparing two instances of the user type. If this method returns false, the entity is marked as dirty, and, when the session is flushed, will trigger an UPDATE. So, in your custom user type, you must implement this carefully so that it is not mistakenly considered changed. For example, you can cache the original column value inside of it, and compare it with the one in the other instance. Let’s see an example implementation of a custom user type that converts a Byte[] from a BLOB column into an Image: 1: [Serializable] 2: public sealed class ImageUserType : IUserType 3: { 4: private Byte[] data = null; 5: 6: public ImageUserType() 7: { 8: this.ImageFormat = ImageFormat.Png; 9: } 10: 11: public ImageFormat ImageFormat 12: { 13: get; 14: set; 15: } 16: 17: public Boolean IsMutable 18: { 19: get 20: { 21: return (true); 22: } 23: } 24: 25: public Object Assemble(Object cached, Object owner) 26: { 27: return (cached); 28: } 29: 30: public Object DeepCopy(Object value) 31: { 32: return (value); 33: } 34: 35: public Object Disassemble(Object value) 36: { 37: return (value); 38: } 39: 40: public new Boolean Equals(Object x, Object y) 41: { 42: return (Object.Equals(x, y)); 43: } 44: 45: public Int32 GetHashCode(Object x) 46: { 47: return ((x != null) ? x.GetHashCode() : 0); 48: } 49: 50: public override Int32 GetHashCode() 51: { 52: return ((this.data != null) ? this.data.GetHashCode() : 0); 53: } 54: 55: public override Boolean Equals(Object obj) 56: { 57: ImageUserType other = obj as ImageUserType; 58: 59: if (other == null) 60: { 61: return (false); 62: } 63: 64: if (Object.ReferenceEquals(this, other) == true) 65: { 66: return (true); 67: } 68: 69: return (this.data.SequenceEqual(other.data)); 70: } 71: 72: public Object NullSafeGet(IDataReader rs, String[] names, Object owner) 73: { 74: Int32 index = rs.GetOrdinal(names[0]); 75: Byte[] data = rs.GetValue(index) as Byte[]; 76: 77: this.data = data as Byte[]; 78: 79: if (data == null) 80: { 81: return (null); 82: } 83: 84: using (MemoryStream stream = new MemoryStream(this.data ?? new Byte[0])) 85: { 86: return (Image.FromStream(stream)); 87: } 88: } 89: 90: public void NullSafeSet(IDbCommand cmd, Object value, Int32 index) 91: { 92: if (value != null) 93: { 94: Image data = value as Image; 95: 96: using (MemoryStream stream = new MemoryStream()) 97: { 98: data.Save(stream, this.ImageFormat); 99: value = stream.ToArray(); 100: } 101: } 102: 103: (cmd.Parameters[index] as DbParameter).Value = value ?? DBNull.Value; 104: } 105: 106: public Object Replace(Object original, Object target, Object owner) 107: { 108: return (original); 109: } 110: 111: public Type ReturnedType 112: { 113: get 114: { 115: return (typeof(Image)); 116: } 117: } 118: 119: public SqlType[] SqlTypes 120: { 121: get 122: { 123: return (new SqlType[] { new SqlType(DbType.Binary) }); 124: } 125: } 126: } In this case, we need to cache the original Byte[] data because it’s not easy to compare two Image instances, unless, of course, they are the same.

    Read the article

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

1 2  | Next Page >