Look at the method [SetEquals][1].

    my_hashset.SetEquals(other);


  [1]: https://msdn.microsoft.com/en-us/library/dd412096(v=vs.110).aspx

    IEqualityComparer&lt;HashSet&lt;int&gt;&gt; comp = HashSet&lt;int&gt;.CreateSetComparer();
    Console.WriteLine(&quot;CreateSetComparer set1 == set2 : {0}&quot;, comp.Equals(set1, set2));
    // or
    bool areEqual = HashSet&lt;int&gt;.CreateSetComparer().Equals(set1, set2);

   

This is a follow up to [this question][1], where I didn&#39;t get any input on this point. Here is the brief question:

**Is it possible to detect and debug problems coming from multi-threaded code?**

Often we have to tell our customers: &quot;We can&#39;t reproduce the problem here, so we can&#39;t fix it. Please tell us the steps to reproduce the problem, then we&#39;ll fix it.&quot; It&#39;s a somehow nasty answer if I know that it is a multi-threading problem, but mostly I don&#39;t. How do I get to know that a problem is a multi-threading issue and how to debug it?

I&#39;d like to know if there are any special logging frameworks, or debugging techniques, or code inspectors, or anything else to help solving such issues. General approaches are welcome. If any answer should be language related then keep it to .NET and Java.

  [1]: https://stackoverflow.com/questions/493311/how-to-write-safe-correct-multi-threaded-code-in-net

How to detect and debug multi-threading problems?

Using TortoiseSVN - when I use Test Merge, I get the error &quot;http://mysvnserver/svn/main/branches/ProjectA must be ancestrally related to http://mysvnserver/svn/main/trunk/ProjectB&quot;

What can I do to resolve this?

SVN - Reintegration Merge error: &quot;must be ancestrally related&quot;

I am trying to determine if two `HashSet` objects in .NET 3.5 (C#) are equal sets, *i.e.* contain the same values. This seems like something one would obviously want to do but none of the provided functions seem to give you this information.

The way I can think to do this is by checking if the count of the two sets are equal *and* one set is a subset (not proper) of the other. I think the only way that can happen is if they are equal sets. Example code:

    HashSet&lt;int&gt; set1 = new HashSet&lt;int&gt;();
    set1.Add(1);
    set1.Add(2);
    set1.Add(3);
    
    HashSet&lt;int&gt; set2 = new HashSet&lt;int&gt;();
    set2.Add(1);
    set2.Add(2);
    set2.Add(3);
    
    if(set1.Count == set2.Count &amp;&amp; set1.IsSubsetOf(set2))
    {
        // do something
    }

Would this always work? Is there a better way? Why doesn&#39;t `HashSet` have a  `public bool IsEqualSetWith()` function?

How do you determine if two HashSets are equal (by value, not by reference)?

I am trying to determine if two <code>HashSet</code> objects in .NET 3.5 (C#) are equal sets, i.e. contain the same values. This seems like something one would obviously want to do but none of the provided functions seem to give you this information.
The way I can think to do this is by checking if the count of the two sets are equal and one set is a subset (not proper) of the other. I think the only way that can happen is if they are equal sets. Example code:
<pre><code class="hljs language-ini">HashSet&#x3C;int> set1 = new HashSet&#x3C;int>();
set1.Add(1);
set1.Add(2);
set1.Add(3);

HashSet&#x3C;int> set2 = new HashSet&#x3C;int>();
set2.Add(1);
set2.Add(2);
set2.Add(3);

if(set1.Count == set2.Count &#x26;&#x26; set1.IsSubsetOf(set2))
{
 // do something
}
</code></pre>
Would this always work? Is there a better way? Why doesn't <code>HashSet</code> have a <code>public bool IsEqualSetWith()</code> function?

I&#39;m writing an integration test where I will be inserting a number of objects into a database and then checking to make sure whether my method retrieves those objects.

My connection to the database is through NHibernate...and my usual method of creating such a test would be to do the following:

    NHibernateSession.BeginTransaction();
    
    //use nhibernate to insert objects into database
    //retrieve objects via my method
    //verify actual objects returned are the same as those inserted
    
    NHibernateSession.RollbackTransaction();

However, I&#39;ve recently found out about [TransactionScope][1] which apparently can be used for this very purpose...

Some [example code I&#39;ve found][2] is as follows:

    public static int AddDepartmentWithEmployees(Department dept)
    {
    
        int res = 0;
    
        DepartmentAdapter deptAdapter = new DepartmentAdapter();
        EmployeeAdapter empAdapter = new EmployeeAdapter();
        using (TransactionScope txScope = new TransactionScope())
        {
    
            res += deptAdapter.Insert(dept.DepartmentName);
            //Custom method made to return Department ID 
            //after inserting the department &quot;Identity Column&quot;
            dept.DepartmentID = deptAdapter.GetInsertReturnValue();
            foreach(Employee emp in dept.Employees)
            {
    
                emp.EmployeeDeptID = dept.DepartmentID;
                res += empAdapter.Insert(emp.EmployeeName, emp.EmployeeDeptID);
    
            }
            txScope.Complete();
    
        }
        return res;
    
    }

I believe that if I don&#39;t include the line `txScope.Complete()` that the data inserted will be rolled back. But unfortunately I don&#39;t understand how that is possible... how does the `txScope` object keep a track of the `deptAdapter` and `empAdapter` objects and their transactions on the database.

I feel like I&#39;m missing a bit of information here...am I really able to replace my `BeginTransaction()` and `RollbackTransaction(`) calls by surrounding my code using `TransactionScope`?

If not, how then does `TransactionScope` work to roll back transactions?

  [1]: http://msdn.microsoft.com/en-us/library/system.transactions.transactionscope.aspx
  [2]: http://dotnetslackers.com/articles/ado_net/Managing_Transactions_using_TransactionScope.aspx

How does TransactionScope roll back transactions?

Why can&#39;t you create a generic indexer in .NET?

the following code throws a compiler error:

    public T this&lt;T&gt;[string key]
    {
        get =&gt; /* Return generic type T. */
    }

Does this mean you can&#39;t create a generic indexer for a generic member collection?

Why it is not possible to define generic indexers in .NET?

I want to use a collection initializer for the next bit of code:

    public Dictionary&lt;int, string&gt; GetNames()
    {
        Dictionary&lt;int, string&gt; names = new Dictionary&lt;int, string&gt;();
        names.Add(1, &quot;Adam&quot;);
        names.Add(2, &quot;Bart&quot;);
        names.Add(3, &quot;Charlie&quot;);
        return names;
    }

So typically it should be something like:

    return new Dictionary&lt;int, string&gt;
    { 
       1, &quot;Adam&quot;,
       2, &quot;Bart&quot;
       ...

But what is the correct syntax for this?



Can I use a collection initializer for Dictionary&lt;TKey, TValue&gt; entries?

I often find myself implementing a class maintaining some kind of own status property as an enum: I have a Status enum and ONE Status property of Status type. How should I solve this name conflict?

    public class Car
    {
      public enum Status
      {
        Off,
        Starting,
        Moving
      };
    
      Status status = Status.Off;
    
      public Status Status // &lt;===== Won&#39;t compile =====
      {
        get { return status; }
        set { status = value; DoSomething(); }
      }
    }

If the Status enum were common to different types, I&#39;d put it outside the class and the problem would be solved. But Status applies to Car only hence it doesn&#39;t make sense to declare the enum outside the class.

What naming convention do you use in this case?

NB: This question was partially debated in comments of an answer of [this question][1]. Since it wasn&#39;t the *main* question, it didn&#39;t get much visibility.

EDIT: Filip Ekberg suggests an IMO excellent workaround for the specific case of &#39;Status&#39;. Yet I&#39;d be interesting to read about solutions where the name of the enum/property is different, as in Michael Prewecki&#39;s *answer*.

EDIT2 (May 2010): My favorite solution is to pluralize the enum type name, as suggested by Chris S. According to MS guidelines, this should be used for flag enums only. But I&#39;ve come to like it more and more. I now use it for regular enums as well.

  [1]: https://stackoverflow.com/questions/211567/enum-and-property-naming-conflicts


C# naming convention for enum and matching property

Expanding upon my [earlier problem][1], I&#39;ve decided to (de)serialize my config file class which worked great. 

I now want to store an associative array of drive letters to map (key is the drive letter, value is the network path) and have tried using `Dictionary`, `HybridDictionary`, and `Hashtable` for this but I always get the following error when calling `ConfigFile.Load()` or `ConfigFile.Save()`:

&gt; There was an error reflecting type
&gt; &#39;App.ConfigFile&#39;. [snip]
&gt; System.NotSupportedException: Cannot
&gt; serialize member
&gt; App.Configfile.mappedDrives [snip]

From what I&#39;ve read Dictionaries and HashTables can be serialized, so what am I doing wrong?

    [XmlRoot(ElementName=&quot;Config&quot;)]
    public class ConfigFile
    {
        public String guiPath { get; set; }
        public string configPath { get; set; }
        public Dictionary&lt;string, string&gt; mappedDrives = new Dictionary&lt;string, string&gt;();

        public Boolean Save(String filename)
        {
            using(var filestream = File.Open(filename, FileMode.OpenOrCreate,FileAccess.ReadWrite))
            {
                try
                {
                    var serializer = new XmlSerializer(typeof(ConfigFile));
                    serializer.Serialize(filestream, this);
                    return true;
                } catch(Exception e) {
                    MessageBox.Show(e.Message);
                    return false;
                }
            }
        }

        public void addDrive(string drvLetter, string path)
        {
            this.mappedDrives.Add(drvLetter, path);
        }

        public static ConfigFile Load(string filename)
        {
            using (var filestream = File.Open(filename, FileMode.Open, FileAccess.Read))
            {
                try
                {
                    var serializer = new XmlSerializer(typeof(ConfigFile));
                    return (ConfigFile)serializer.Deserialize(filestream);
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message + ex.ToString());
                    return new ConfigFile();
                }
            }
        }
    }


  [1]: https://stackoverflow.com/questions/489173/writing-xml-with-c

Serialize Class containing Dictionary member

Is there a library or a class/function that I can use to convert an integer to it&#39;s verbal representation?

Example input:

&gt;4,567,788`

Example output:

&gt;Four million, Five hundred sixty-seven thousand, seven hundred eighty-eight


  [1]: http://stackoverflow.com/questions/3213/c-convert-integers-into-written-numbers

How can I convert an integer into its verbal representation?

I have a the following dictionary:

    IDictionary&lt;int, IList&lt;MyClass&gt;&gt; myDictionary 

and I am wanting to get all the values in the dictionary as an IList&lt;MyClass&gt;....


----------


Just to add a bit of a background as to how I&#39;ve gotten into this situation....

I have a method that gets me a list of MyClass. I then have another method that converts that list into a dictionary where they key is the id for MyClass. Later on...and without access to that original list...I&#39;m needing to obtain the original ungrouped list of MyClass.


----------


When I pass myDictionary.Values.ToList() to a method that takes an IList&lt;MyClass&gt; I get a compile error that says that it can&#39;t convert from 

    System.Collections.Generic.List&lt;System.Collections.Generic.IList&lt;MyClass&gt;&gt; 

to:

    System.Collections.Generic.IList&lt;MyClass&gt;

Now, I can understand that its gone and added each of the groups of IList&lt;MyClass&gt; to the new list as separate elements of the list....but in this instance its not really what I&#39;m after. I just want a list of all the values in the entire dictionary.

How then can I get what I&#39;m after without looping through each of the key values in the dictionary and creating the list I want?


How do I get all the values of a Dictionary&lt;TKey, TValue&gt; as an IList&lt;TValue&gt;?

Is there any easy LINQ expression to concatenate my entire `List&lt;string&gt;` collection items to a single `string` with a delimiter character?

What if the collection is of custom objects instead of `string`? Imagine I need to concatenate on `object.Name`.




Concat all strings inside a List&lt;string&gt; using LINQ

The default databinding on `TextBox` is `TwoWay` and it commits the text to the property only when `TextBox` lost its focus.

Is there any easy XAML way to make the databinding happen when I press the &lt;kbd&gt;Enter&lt;/kbd&gt; key on the `TextBox`?. I know it is pretty easy to do in the code behind, but imagine if this `TextBox` is inside some complex `DataTemplate`.

Bind TextBox on Enter-key press

I have a generic method which has two generic parameters. I tried to compile the code below but it doesn&#39;t work. Is it a .NET limitation? Is it possible to have multiple constraints for different parameter?

    public TResponse Call&lt;TResponse, TRequest&gt;(TRequest request)
      where TRequest : MyClass, TResponse : MyOtherClass


Generic method with multiple constraints

**EDIT**: Re-written this question based on original answer

The `scala.collection.immutable.Set` class is not covariant in its type parameter. Why is this? 

    import scala.collection.immutable._

    def foo(s: Set[CharSequence]): Unit = {
        println(s)
    }

    def bar(): Unit = {
       val s: Set[String] = Set(&quot;Hello&quot;, &quot;World&quot;);
       foo(s); //DOES NOT COMPILE, regardless of whether type is declared 
               //explicitly in the val s declaration
    }



Why is Scala&#39;s immutable Set not covariant in its type?

Do you know some neat Java libaries that allow you to make cartesian product of two (or more) sets? 

For example: I have three sets. One with objects of class Person, second with objects of class Gift and third with objects of class GiftExtension.

I want to generate one set containing all possible triples Person-Gift-GiftExtension.

The number of sets might vary so I cannot do this in nested foreach loop. 
Under some conditions my application needs to make a product of Person-Gift pair, sometimes it is triple Person-Gift-GiftExtension, sometimes there might even be sets Person-Gift-GiftExtension-GiftSecondExtension-GiftThirdExtension, etc. 

Cartesian product of an arbitrary number of sets

I am not sure if this is possible but I want to iterate through a class and set a field member property without referring to the field object explicitly:

    public class Employee
    {
      public Person _person = new Person();
    	
      public void DynamicallySetPersonProperty()
      {
        MemberInfo[] members = this.GetType().GetMembers();
    
        foreach (MemberInfo member in members.Where(a =&gt; a.Name == &quot;_person&quot;))
        //get the _person field
        {
    
          Type type = member.GetType();
          PropertyInfo prop = type.GetProperty(&quot;Name&quot;); //good, this works, now to set a value for it
    
          //this line does not work - the error is &quot;property set method not found&quot;
          prop.SetValue(member, &quot;new name&quot;, null);
        }
      }
    }
    
    
    public class Person
    {
      public string Name { get; set; }
    }



In the answer that I marked as the answer you need to add:

      public static bool IsNullOrEmpty(this string source)
      {
        return (source == null || source.Length &gt; 0) ? true : false;
      }


c# - How to iterate through classes fields and set properties

I&#39;m sure there&#39;s a good reason, but could someone please explain why the `java.util.Set` interface lacks `get(int Index)`, or any similar `get()` method?

It seems that sets are great for putting things into, but I can&#39;t find an elegant way of retrieving a single item from it.

If I know I want the first item, I can use `set.iterator().next()`, but otherwise it seems I have to cast to an Array to retrieve an item at a specific index?

What are the appropriate ways of retrieving data from a set? (other than using an iterator)

I&#39;m sure the fact that it&#39;s excluded from the API means there&#39;s a good reason for not doing this -- could someone please enlighten me?

**EDIT:**
Some extremely great answers here, and a few saying &quot;more context&quot;.  The specific scenario was a dbUnit test, where I could reasonably assert that the returned set from a query had only 1 item, and I was trying to access that item.

However, the question is more valid without the scenario, as it remains more focussed:

*What&#39;s the difference between set and list*.

Thanks to all for the fantastic answers below.

Why doesn&#39;t java.util.Set have get(int index)?

What is the fundamental difference between the `Set&lt;E&gt;` and `List&lt;E&gt;` interfaces?

What is the difference between Set and List?

Does the [`HashSet`](https://msdn.microsoft.com/en-us/library/bb359438(v=vs.110).aspx) collection introduced in .NET 3.5 preserve insertion order when iterated using `foreach`? 

The [documentation][1] states, that the collection is not sorted, but it doesn&#39;t say anything about insertion order. A pre-release BCL [blog entry][2] states that it is unordered, but [this article][3] states that it is designed to preserve insertion order. My limited testing suggests, that order is preserved, but that could be a coincidence.

  [1]: http://msdn.microsoft.com/en-us/library/bb397727.aspx
  [2]: http://blogs.msdn.com/bclteam/archive/2006/11/09/introducing-hashset-t-kim-hamilton.aspx
  [3]: http://www.vcskicks.com/hashset.php

Does HashSet preserve insertion order?

So, if I try to remove elements from a Java *HashSet* while iterating, I get a *ConcurrentModificationException*.  What is the best way to remove a subset of the elements from a *HashSet* as in the following example?

    Set&lt;Integer&gt; set = new HashSet&lt;Integer&gt;();
    
    for(int i = 0; i &lt; 10; i++)
    	set.add(i);
    
    // Throws ConcurrentModificationException
    for(Integer element : set)
    	if(element % 2 == 0)
    		set.remove(element);

Here is a solution, but I don&#39;t think it&#39;s very elegant:
    
    Set&lt;Integer&gt; set = new HashSet&lt;Integer&gt;();
    Collection&lt;Integer&gt; removeCandidates = new LinkedList&lt;Integer&gt;();
    
    for(int i = 0; i &lt; 10; i++)
    	set.add(i);
    
    for(Integer element : set)
    	if(element % 2 == 0)
    		removeCandidates.add(element);
    
    set.removeAll(removeCandidates);

Thanks!


Remove Elements from a HashSet while Iterating

I am exploring the `HashSet&lt;T&gt;` type, but I don&#39;t understand where it stands in collections.

Can one use it to replace a `List&lt;T&gt;`? I imagine the performance of a `HashSet&lt;T&gt;` to be better, but I couldn&#39;t see individual access to its elements.

Is it only for enumeration?

When should I use the HashSet&lt;T&gt; type?

I&#39;ve always loved trees, that nice `O(n*log(n))` and the tidiness of them. However, every software engineer I&#39;ve ever known has asked me pointedly why I would use a `TreeSet`. From a CS background, I don&#39;t think it matters all that much which you use, and I don&#39;t care to mess around with hash functions and buckets (in the case of `Java`).

In which cases should I use a `HashSet` over a `TreeSet`?

Hashset vs Treeset

I need a HashSet that preserves insertion ordering, are there any implementations of this in the framework?

Content Type	Original Author	Original Content on Stackoverflow
Question	Craig W	View Question on Stackoverflow
Solution 1 - C#	Michael Burr	View Answer on Stackoverflow
Solution 2 - C#	Gregory Adam	View Answer on Stackoverflow

How do you determine if two HashSets are equal (by value, not by reference)?

C# Problem Overview

C# Solutions

Solution 1 - C#

Solution 2 - C#

SVN - Reintegration Merge error: "must be ancestrally related"

How to detect and debug multi-threading problems?

Attributions