gethashcode

A glance at the source code for string.GetHashCode using Reflector reveals the following (for mscorlib.dll version 4.0): public override unsafe int GetHashCode() { fixed (char* str = ((char*) this)) { char* chPtr = str; int num = 0x15051505; int num2 = num; int* numPtr = (int*) chPtr; for (int i = this.Length; i > 0; i -= 4) { num = (((num << 5) + num) + (num >> 0x1b)) ^ numPtr[0]; if (i <= 2) { break; } num2 = (((num2 << 5) + num2) + (num2 >> 0x1b)) ^ numPtr[1]; numPtr += 2; } return (num + (num2 * 0x5d588b65)); } } Now, I realize that the implementation of GetHashCode is not specified and is

This question already has an answer here: What is the best algorithm for an overridden System.Object.GetHashCode? 19 answers As you know, GetHashCode returns a semi-unique value that can be used to identify an object instance in a collection. As a good practice, it is recommended to override this method and implement your own. My question is - do you override this method when working on custom objects? If so, what algorithm do you use to generate the unique ID? I was thinking about generating a GUID and then getting integer data from that identificator. When you override GetHashCode() you also

After reading all the questions and answers on StackOverflow concerning overriding GetHashCode() I wrote the following extension method for easy and convenient overriding of GetHashCode() : public static class ObjectExtensions { private const int _seedPrimeNumber = 691; private const int _fieldPrimeNumber = 397; public static int GetHashCodeFromFields(this object obj, params object[] fields) { unchecked { //unchecked to prevent throwing overflow exception int hashCode = _seedPrimeNumber; for (int i = 0; i < fields.Length; i++) if (fields[i] != null) hashCode *= _fieldPrimeNumber + fields[i]

The Help says this: Anonymous types are class types that derive directly from object, and that cannot be cast to any type except object. The compiler provides a name for each anonymous type, although your application cannot access it. From the perspective of the common language runtime, an anonymous type is no different from any other reference type. If two or more anonymous object initializers in an assembly specify a sequence of properties that are in the same order and that have the same names and types, the compiler treats the objects as instances of the same type. They share the same

This question already has an answer here: How do I create a HashCode in .net (c#) for a string that is safe to store in a database? 3 answers I want to generate an integer hashcode for strings, that will stay constant forever; i.e. the same string should always result in the same hashcode. The hash does not have to be cryptographically secure, it will not be used for passwords or sensitive data. My first attempt was to use the .net framework string.GetHashCode() function. However upon reading the sources I found the following commment: // We want to ensure we can change our hash function daily

I am porting something from Java to C#. In Java the hashcode of a ArrayList depends on the items in it. In C# I always get the same hashcode from a List ... Why is this? For some of my objects the hashcode needs to be different because the objects in their list property make the objects non-equal. I would expect that a hashcode is always unique for the object's state and only equals another hashcode when the object is equal. Am I wrong? In order to work correctly, hashcodes must be immutable – an object's hash code must never change. If an object's hashcode does change, any dictionaries