I have a strange problem and it's been frustrating me for the past few hours. I can't seem to find anything related; perhaps I'm not being specific enough, as I'm not sure how to word it correctly, or it's a strangely unique problem. There's a form a user fills in to update their account information, everything works as it should, except for one text area. This text a
我有一个奇怪的问题,在过去的几个小时里,我感到很沮丧。 我似乎无法找到任何相关的东西; 也许我没有足够具体,因为我不知道如何正确地说出它,或者这是一个奇怪的独特问题。 用户填写更新帐户信息的表单,除了一个文本区域外,其他所有内容都可以正常工作。 一旦表单被POST,这个文本区域'(绑定到UserInfo属性Comments )的值就变为null。 Comments属性是唯一的属性是null。 何时发生 A)没有现有值,用户输入
A coworker asked me today how to add a range to a collection. He has a class that inherits from Collection<T> . There's a get-only property of that type that already contains some items. He wants to add the items in another collection to the property collection. How can he do so in a C#3-friendly fashion? (Note the constraint about the get-only property, which prevents solutions li
今天一位同事问我如何在一个系列中增加一个范围。 他有一个继承自Collection<T> 。 有一种只包含某些项目的只能获取属性。 他想将另一个集合中的项目添加到属性集合中。 他如何以C#3友好的方式来做到这一点? (请注意关于只读属性的约束,这会阻止像联合和重新分配这样的解决方案。) 当然,与财产的foreach。 添加将工作。 但是List<T> -style AddRange会更加优雅。 编写扩展方法很简单: public stat
What is the fastest way to implement a new class that inherits from List<T> ? class Animal {} class Animals : List<Animal> {} // (1) One problem I've encountered: By simply doing (1) , I've found that I'm not getting the benefit of inheriting any constructors from List<T> . In the end, I'd like Animals to behave a lot like a List<T> (eg, can be constru
实现从List<T>继承的新类的最快方法是什么? class Animal {} class Animals : List<Animal> {} // (1) 我遇到的一个问题:通过简单地做(1) ,我发现我没有从List<T>继承任何构造函数的好处。 最后,我希望Animals行为很像List<T> (例如,可以构建,与Linq兼容)。 但除此之外,我还希望能够添加自己的自定义方法。 如果你想创建一个公开暴露的动物集合,你不应该从List<T>继承,而应
This question already has an answer here: Null Conditional Operators 2 answers This is the null conditional operator: Used to test for null before performing a member access (?.) or index (?[) operation. You method's code without the use of null conditional operator it could be written as below: public void DoSomething(Result result) { if(result!=null) { if(result.Act
这个问题在这里已经有了答案: 空条件运算符2个答案 这是空的条件运算符: 用于在执行成员访问(?。)或索引(?[)操作之前测试null。 你的方法的代码不使用空条件运算符,它可以写成如下: public void DoSomething(Result result) { if(result!=null) { if(result.Actions!=null) { return result.Actions.Utterance; } else { return nul
This question already has an answer here: What does the question mark in member access mean in C#? 2 answers What do two question marks together mean in C#? 16 answers What is the purpose of a question mark after a type (for example: int? myVariable)? 8 answers Benefits of using the conditional ?: (ternary) operator 16 answers Question marks have different meaning in C# depending on
这个问题在这里已经有了答案: 成员访问中的问号在C#中意味着什么? 2个答案 C#中两个问号在一起意味着什么? 16个答案 类型之后的问号的目的是什么(例如:int?myVariable)? 8个答案 :使用条件?:(三元)操作符的好处16答案 问号在C#中的含义取决于上下文。 空条件运算符 (MSDN,C#中成员访问中的问号是什么意思?) Console.Write(myObject?.Items?[0].ToString()); 条件运算符/三元运算符 (MSDN,
Googling is only coming up with the keyword, but I stumbled across some code that says MyVariable = default(MyObject); and I am wondering what it means... For a reference-type, it returns null For a value-type other than Nullable<T> it returns a zero-initialized value For Nullable<T> it returns the empty (pseudo-null) value (actually, this is a re-statement of the second bulle
谷歌搜索只是关键字,但我偶然发现了一些代码说 MyVariable = default(MyObject); 我想知道这意味着什么... 对于引用类型,它返回null 对于Nullable<T>以外的值类型,它返回一个零初始值 对于Nullable<T>它返回空(伪空)值(实际上,这是第二个项目符号的重新声明,但值得明确) default(T)的最大用途是泛型,像Try...模式: bool TryGetValue(out T value) { if(NoDataIsAvailable) { value
Possible Duplicates: ?? Null Coalescing Operator --> What does coalescing mean? What do two question marks together mean in C#? I couldn't find this question being asked here so I figured I would ask it. What does a double question mark do in C#? Example: x = y ?? z; This is a null coalescing operator. The method above states x is assigned y's value, unless y is null, in w
可能重复: ?? 空合并运算符 - >合并意味着什么? C#中两个问号在一起意味着什么? 我找不到这个问题,所以我想我会问这个问题。 双重问号在C#中做什么? 例: x = y ?? z; 这是一个空合并运算符。 上面的方法状态x被分配了y的值,除非y为空,在这种情况下,它被分配了z的值。 如果不是null,则使用y,否则使用z 维基百科: 这是空合并操作符和简写: x = (y != null ? y : z);
Possible Duplicate: Use of var keyword in C# After discussion with colleagues regarding the use of the 'var' keyword in C# 3 I wondered what people's opinions were on the appropriate uses of type inference via var? For example I rather lazily used var in questionable circumstances, eg:- foreach(var item in someList) { // ... } // Type of 'item' not clear. var something = someOb
可能重复: 在C#中使用var关键字 在与同事讨论在C#3中使用'var'关键字之后,我想知道人们对通过var?进行类型推断的适当用法有何看法? 例如,我比较懒惰地在可疑情况下使用var,例如: - foreach(var item in someList) { // ... } // Type of 'item' not clear. var something = someObject.SomeProperty; // Type of 'something' not clear. var something = someMethod(); // Type of 'something' not clea
什么时候应该使用退货率,何时只能使用退货? yield结构用于创建一个可以连续生成多个值的迭代器: IEnumerable<int> three_numbers() { yield return 1; yield return 2; yield return 3; } ... foreach (var i in three_numbers()) { // i becomes 1, 2 and 3, in turn. } Use yield when you are returning an enumerable, and you don't have all the results at that point. Practically, I
什么时候应该使用退货率,何时只能使用退货? yield结构用于创建一个可以连续生成多个值的迭代器: IEnumerable<int> three_numbers() { yield return 1; yield return 2; yield return 3; } ... foreach (var i in three_numbers()) { // i becomes 1, 2 and 3, in turn. } 当你返回一个可枚举的时候使用yield,并且你没有那个时候的所有结果。 实际上,当我想要遍历大块信息(数据库,平面文件等)时
In my everlasting quest to suck less I'm trying to understand the "yield" statement, but I keep encountering the same error. The body of [someMethod] cannot be an iterator block because 'System.Collections.Generic.List< AClass>' is not an iterator interface type. This is the code where I got stuck: foreach (XElement header in headersXml.Root.Elements()){ yield
在我永恒的追求吮吸少我试图理解“收益”的声明,但我不断遇到同样的错误。 [someMethod]的主体不能是迭代器块,因为'System.Collections.Generic.List <AClass>'不是迭代器接口类型。 这是我卡住的代码: foreach (XElement header in headersXml.Root.Elements()){ yield return (ParseHeader(header)); } 我究竟做错了什么? 我不能在迭代器中使用yield吗? 那有什么意义? 在这个