英文:
Not throwing exception when object is null
问题
public class Stack
{
public readonly Stack
public void Push(object obj)
{
if (obj == null)
{
throw new InvalidOperationException("您不能将空对象添加到堆栈");
}
string foodObject = obj.ToString();
foodStack.Push(foodObject);
}
}
主要方法：
Stack item1 = new Stack();
item1.Push(null);
我尝试过更改异常的类型。
英文:
So I created a basic stack which takes in a string and gets passed in an object. I want to make sure that if the object being passed in is null, it throws an exception. However when I pass in a null object, the exception doesn't get thrown and can't see why.
public class Stack
{
public readonly Stack<string> foodStack = new Stack<string>();
public void Push(object obj)
{
if (obj == null)
{
throw new InvalidOperationException("You cannot add null to the stack");
}
string foodObject = obj.ToString();
foodStack.Push(foodObject);
}
Main Method:
Stack item1 = new Stack();
item1.Push(null);
I have tried changing the type of exception.
答案1
得分: 1
你的环境/目标是什么？
// .NET FW 4.8, C# 5.0
using System;
using System.Collections.Generic;
namespace NsCustomStack {
public class Astack {
public readonly Stack<string> foodStack = new Stack<string>();
public void Push(object obj) {
if (obj == null) {
throw new InvalidOperationException("You cannot add null to the stack");
}
string foodObject = obj.ToString();
foodStack.Push(foodObject);
}
}
class CustomStack {
static void Main() {
Astack item1 = new Astack(); item1.Push(null);
}
}
}
结果：
未处理的异常: System.InvalidOperationException: 不能向堆栈中添加空值
___ 在 NsCustomStack.Astack.Push(Object obj) 中
___ 在 NsCustomStack.CustomStack.Main() 中
更新 我的猜测是
Stack item1 = new Stack();
item1.Push(null);
使用了 System.Collections.Stack，其 Push 方法接受空值。
解决方案可以是使用完全限定的名称来引用您的自定义 Stack：
var item1 = new YourNamespace.Stack();
item1.Push(null);
我使用以下代码模拟了此问题：
using System.Collections;
namespace ConsoleApp3Classes {
public class Stack {
public readonly Stack<string> foodStack = new Stack<string>();
public void Push(object obj) {
if (obj is null) {
throw new ArgumentNullException(nameof(obj), "不能向堆栈中添加空值");
}
string foodObject = obj.ToString();
foodStack.Push(foodObject);
}
}
}
namespace ConsoleApp3 {
internal class Program {
static void Main(string[] args) {
var item1 = new Stack(); item1.Push(null);
var item1a = new ConsoleApp3Classes.Stack(); item1a.Push(null);
}
}
}
var item1 = new Stack(); item1.Push(null); 不会生成异常，而下一行会生成异常。
英文:
What's your environment/target?
// .NET FW 4.8, C# 5.0
using System;
using System.Collections.Generic;
namespace NsCustomStack {
public class Astack {
public readonly Stack<string> foodStack = new Stack<string>();
public void Push(object obj) {
if (obj == null) {
throw new InvalidOperationException("You cannot add null to the stack");
}
string foodObject = obj.ToString();
foodStack.Push(foodObject);
}
}
class CustomStack {
static void Main() {
Astack item1 = new Astack(); item1.Push(null);
}
}
}
Result:
Unhandled Exception: System.InvalidOperationException: You cannot add null to the stack
___ at NsCustomStack.Astack.Push(Object obj)
___ at NsCustomStack.CustomStack.Main()
UPD My guess is
Stack item1 = new Stack();
item1.Push(null);
uses System.Collections.Stack which Push method accepts null.
The solution can be to use the fully qualified name for your custom Stack:
var item1 = new YourNamespace.Stack();
item1.Push(null);
I simulated the issue with this code:
using System.Collections;
namespace ConsoleApp3Classes {
public class Stack {
public readonly Stack<string> foodStack = new Stack<string>();
public void Push(object obj) {
if (obj is null) {
throw new ArgumentNullException(nameof(obj), "You cannot add null to the stack");
}
string foodObject = obj.ToString();
foodStack.Push(foodObject);
}
}
}
namespace ConsoleApp3 {
internal class Program {
static void Main(string[] args) {
var item1 = new Stack(); item1.Push(null);
var item1a = new ConsoleApp3Classes.Stack(); item1a.Push(null);
}
}
}
"var item1 = new Stack(); item1.Push(null);" doesn't generate the exception while the next line does.
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