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• Nullable Type implementation without nullable feature of C#

  - by koumides

  How can we implement a nullable type in C# if we didn't have this feature in C#?

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• Nullable types and ?? operator C# [en-US]

  - by ruimachado

  Nullable types vs Non-nullable types   While developing our C# projects its frequent the null comparison operation to avoid null exceptions. This simple operation is mainly coded using the "var x = null" code example inside an if clause. However not all types of variables are nullable, which means that setting a variable to null is not…

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• Nullable Enum nullable type question

  - by Michael Kniskern

  I get the following compilation error with the following source code: Compilation Error: Type of conditional expression cannot be determined because there is no implicit conversion between '' and 'MyEnum' Source Code public enum MyEnum { Value1, Value2, Value3 } public class MyClass { public MyClass() {} public MyEnum?…

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• C#/.NET Little Wonders: The Nullable static class

  - by James Michael Hare

  Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. Today we’re going to look at an interesting Little Wonder that can be used to mitigate what…

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• Where in memory are stored nullable types?

  - by Ondrej Slinták

  This is maybe a follow up to question about nullable types. Where exactly are nullable value types (int?...) stored in memory? First I thought it's clear enough, as Nullable<T> is struct and those are value types. Then I found Jon Skeet's article "Memory in .NET", which says: Note that a value type variable can never have…

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• FluentNHibernate: Not.Nullable() doesn't affect output schema

  - by alex

  Hello I'm using fluent nhibernate v. 1.0.0.595. There is a class: public class Weight { public virtual int Id { get; set; } public virtual double Value { get; set; } } I want to map it on the following table: create table [Weight] ( WeightId INT IDENTITY NOT NULL, Weight DOUBLE not null, primary key (WeightId)…

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• How to compare nullable types?

  - by David_001

  I have a few places where I need to compare 2 (nullable) values, to see if they're the same. I think there should be something in the framework to support this, but can't find anything, so instead have the following: public static bool IsDifferentTo(this bool? x, bool? y) { return (x.HasValue != y.HasValue) ? true : x.HasValue…

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• Why shouldn't I always use nullable types in C#.

  - by Matthew Vines

  I've been searching for some good guidance on this since the concept was introduced in .net 2.0. Why would I ever want to use non-nullable data types in c#? (A better question is why wouldn't I choose nullable types by default, and only use non-nullable types when that explicitly makes sense.) Is there a 'significant' performance…

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• Nullable enum in html helper

  - by Fabien Piron

  I have a view model that contains enum with nullable type like this one : public StudyLevel? studyLevel { get; set; } I have made custom html helper to display a dropdownlist for rendering the enum into the view, the nullable case is displayed using <option value="null">No value</option> the problem is that when i…

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• When should one use nullable types in c#?

  - by Pandiya Chendur

  I have been repeatedly asked these question in many interviews.... But still can't able to explain them with a simple example... What is nullable types in c#?When should one use nullable types in c#?Any simple ex? Any suggestion....

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• Nullable<> as TModel for ViewPage

  - by Alexander Prokofyev

  What are the possible reasons what Nullable<> types are disallowed to be passed as TModel parameter of System.Web.Mvc.ViewPage<TModel> generic? This could be handy sometimes. In ASP.NET MVC source defined what TModel should be a class: public class ViewPage<TModel> : ViewPage where TModel : class but Nullable…

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• Probably silly question about Nullable in .NET

  - by Andrew

  Here is example from J. Richter book "CLR via C#": Nullable<Int32> y = null; How exactly this works? Nullable is a struct, and I can not figure out is this compiler special support or implicit boxing of null value or something else.

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• Having an issue with Nullable MySQL columns in SubSonic 3.0 templates

  - by omegawkd

  Looking at this line in the Settings.ttinclude string CheckNullable(Column col){ string result=""; if(col.IsNullable && col.SysType !="byte[]" && col.SysType !="string") result="?"; return result; } It describes how it determines if the column is nullable based on requirements and returns…

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• Order by nullable property simultaneously with ordering by not nullable property in HQL

  - by Episodex

  Hi, I have a table called Users in my database. Let's assume that User has only 3 properties int ID; string? Name; string Login; If user doesn't specify his name then Login is displayed. Otherwise Name is displayed. I wan't to get list of all users sorted by what is displayed. So if user specified Name, it is taken into…

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• How to parse a string into a nullable int in C# (.NET 3.5)

  - by Glenn Slaven

  I'm wanting to parse a string into a nullable int in C#. ie. I want to get back either the int value of the string or null if it can't be parsed. I was kind of hoping that this would work int? val = stringVal as int?; But that won't work, so the way I'm doing it now is I've written this extension method public static…

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• Confusion about Nullable<T> constraints

  - by n535

  Greetings everybody. I am sorry, if this was already asked before (searched in vain) or is really very simple, but i just can't get it. The MSDN definition of a Nullable type, states, that it is defined in a following manner: [SerializableAttribute] public struct Nullable<T> where T : struct, new() So the question…

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• Are nullable types preferable to magic numbers?

  - by Matt H

  I have been having a little bit of a debate with a coworker lately. We are specifically using C#, but this could apply to any language with nullable types. Say for example you have a value that represents a maximum. However, this maximum value is optional. I argue that a nullable number would be preferable. My…

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• LINQ-to-SQL IN/Contains() for Nullable<T>

  - by Craig Walker

  I want to generate this SQL statement in LINQ: select * from Foo where Value in ( 1, 2, 3 ) The tricky bit seems to be that Value is a column that allows nulls. The equivalent LINQ code would seem to be: IEnumerable<Foo> foos = MyDataContext.Foos; IEnumerable<int> values = GetMyValues(); var myFoos…

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• Nullable<T> as a parameter

  - by ferch

  I alredy have this: public static object GetDBValue(object ObjectEvaluated) { if (ObjectEvaluated == null) return DBNull.Value; else return ObjectEvaluated; } used like: List<SqlParameter> Params = new List<SqlParameter>(); Params.Add(new SqlParameter("@EntityType",…

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• Setting Nullable Integer to String Containing Nothing yields 0

  - by Brian MacKay

  I've been pulling my hair out over some unexpected behavior from nullable integers. If I set an Integer to Nothing, it becomes Nothing as expected. If I set an Integer? to a String that is Nothing, it becomes 0! Of course I get this whether I explicitly cast the String to Integer? or…

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• Checking if Type instance is a nullable enum in C#

  - by adrin

  How do i check if a Type is a nullable enum in C# something like Type t = GetMyType(); bool isEnum = t.IsEnum; //Type member bool isNullableEnum = t.IsNullableEnum(); How to implement this extension method?

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• Performance surprise with "as" and nullable types

  - by Jon Skeet

  I'm just revising chapter 4 of C# in Depth which deals with nullable types, and I'm adding a section about using the "as" operator, which allows you to write: object o = ...; int? x = o as int?; if (x.HasValue) { ... // Use x.Value in here } I thought this was really neat, and that…

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• Using nullable types in C#

  - by Martin Brown

  I'm just interested in people's opinions. When using nullable types in C# what is the best practice way to test for null: bool isNull = (i == null); or bool isNull = !i.HasValue; Also when assigning to a non-null type is this: long? i = 1; long j = (long)i; better than: long? i…

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• Binding a nullable int to an asp:TextBox

  - by Slauma

  I have a property int? MyProperty as a member in my datasource (ObjectDataSource). Can I bind this to a TextBox, like <asp:TextBox ID="MyTextBox" runat="server" Text='<%# Bind("MyProperty") %>' /> Basically I want to get a null value displayed as blank "" in the TextBox,…

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• WPF Toolkit: Nullable object must have a value

  - by Via Lactea

  Hi All, I am trying to create some line charts from a dataset and getting an error (WPF+WPF Toolkit + C#): Nullable object must have a value Here is a code that I use to add some data points to the chart: ObservableCollection points = new ObservableCollection(); foreach…

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