Use the `ToDictionary` method directly.

    var result = 
      // as Jon Skeet pointed out, OrderBy is useless here, I just leave it 
      // show how to use OrderBy in a LINQ query
      myClassCollection.OrderBy(mc =&gt; mc.SomePropToSortOn)
                       .ToDictionary(mc =&gt; mc.KeyProp.ToString(), 
                                     mc =&gt; mc.ValueProp.ToString(), 
                                     StringComparer.OrdinalIgnoreCase);

Look at the `ToLookup` and/or `ToDictionary` extension methods.

I am doing a `find` and then getting a list of files. How do I pipe it to another utility like `cat` (so that cat displays the contents of all those files) and basically need to `grep` something from these files.

How to pipe list of files returned by find command to cat to view all the files

I&#39;m trying to understand Python&#39;s approach to variable scope. In this example, why is `f()` able to alter the value of `x`, as perceived within `main()`, but not the value of `n`?

    def f(n, x):
        n = 2
        x.append(4)
        print(&#39;In f():&#39;, n, x)
    
    def main():
        n = 1
        x = [0,1,2,3]
        print(&#39;Before:&#39;, n, x)
        f(n, x)
        print(&#39;After: &#39;, n, x)
    
    main()

Output:

    Before: 1 [0, 1, 2, 3]
    In f(): 2 [0, 1, 2, 3, 4]
    After:  1 [0, 1, 2, 3, 4]


Why can a function modify some arguments as perceived by the caller, but not others?

I have a collection of MyClass that I&#39;d like to query using LINQ to get distinct values, and get back a Dictionary&amp;lt;string, string&gt; as the result, but I can&#39;t figure out how I can do it any simpler than I&#39;m doing below.  What would some cleaner code be that I can use to get the Dictionary&amp;lt;string, string&gt; as my result?

    var desiredResults = new Dictionary&lt;string, string&gt;(StringComparer.OrdinalIgnoreCase);

    var queryResults = (from MyClass mc in myClassCollection
                        orderby bp.SomePropToSortOn
                        select new KeyValuePair&lt;string, string&gt;(mc.KeyProp, mc.ValueProp)).Distinct();

    foreach (var item in queryResults)
    {
        desiredResults.Add(item.Key.ToString(), item.Value.ToString());
    }


LINQ query to return a Dictionary&lt;string, string&gt;

I have a collection of MyClass that I'd like to query using LINQ to get distinct values, and get back a Dictionary&#x3C;string, string> as the result, but I can't figure out how I can do it any simpler than I'm doing below. What would some cleaner code be that I can use to get the Dictionary&#x3C;string, string> as my result?
<pre><code class="hljs language-csharp">var desiredResults = new Dictionary&#x3C;string, string>(StringComparer.OrdinalIgnoreCase);

var queryResults = (from MyClass mc in myClassCollection
 orderby bp.SomePropToSortOn
 select new KeyValuePair&#x3C;string, string>(mc.KeyProp, mc.ValueProp)).Distinct();

foreach (var item in queryResults)
{
 desiredResults.Add(item.Key.ToString(), item.Value.ToString());
}
</code></pre>

Is there a way to display the lines in the stack trace for the .NET assembly build/deployed in Release mode?

&lt;b&gt;UPDATE:&lt;/b&gt; 

My application is divided into three class library projects and one ASP.NET &quot;website&quot; project.  The error I am trying to track down is in one of the three class library projects.  I only deployed the pdb file for the class library project that is generating the &quot;Object reference not set to an instance of an object&quot; error.

The line numbers are still not showing up in the stack trace.  Do I need to deploy the pdb files for all projects to get the line numbers in the stack trace?

&lt;b&gt;Working solution&lt;/b&gt;

Deploying the pdb file for each application fixed the line number issue.

Display lines number in Stack Trace for .NET assembly in Release mode

What follows is a typical dispose pattern example:

     public bool IsDisposed { get; private set; }
    
      #region IDisposable Members
    
      public void Dispose()
      {
        Dispose(true);
        GC.SuppressFinalize(this);
      }
    
      protected virtual void Dispose(bool disposing)
      {
        if (!IsDisposed)
        {
          if (disposing)
          {
            //perform cleanup here
          }
    
          IsDisposed = true;
        }
      }
    
      ~MyObject()
      {
        Dispose(false);
      }

I understand what dispose does, but what I don&#39;t understand is why you would want to call dispose(false) in the destructor? If you look at the definition it would do absolutely nothing, so why would anyone write code like this? Wouldn&#39;t it make sense to just *not* call dispose from the destructor at all?

Why call dispose(false) in the destructor?

Is there a short way of converting a strongly typed `List&lt;T&gt;` to an Array of the same type, e.g.: `List&lt;MyClass&gt;` to `MyClass[]`?

By short i mean one method call, or at least shorter than:

    MyClass[] myArray = new MyClass[list.Count];
    int i = 0;
    foreach (MyClass myClass in list)
    {
        myArray[i++] = myClass;
    }

Conversion from List&lt;T&gt; to array T[]

I&#39;m wondering if there are any reasons (apart from tidying up source code) why developers use the &quot;Remove Unused `Usings`&quot; feature in Visual Studio 2008?


Why remove unused using directives in C#?

Is there a built in linq method thing I can use to find out if two sequences contains the same items, not taking the order into account?

For example:

    {1, 2, 3} == {2, 1, 3}
    {1, 2, 3} != {2, 1, 3, 4}
    {1, 2, 3} != {1, 2, 4}

You have the SequenceEquals, but then I would have to Order both sequences first, wouldn&#39;t I?

C#: Compare contents of two IEnumerables

I know the following is not possible because the Enumeration&#39;s type has to be an int

    enum GroupTypes
    {
        TheGroup = &quot;OEM&quot;,
        TheOtherGroup = &quot;CMB&quot;
    }

From my database I get a field with incomprehensive codes (the `OEM` and `CMB`s). I would want to make this field into an `enum` or something else understandable. Because if the target is readability, the solution should be terse.

What other options do I have? 

Associating enums with strings in C#

I know that the following is case sensitive:

    if (StringA == StringB) {

So is there an operator which will compare two strings in an insensitive manner?

Is there a C# case insensitive equals operator?

I am beginning to use LINQ in general (so far toXML and toSQL). I&#39;ve seen that sometimes there are two or more ways to achieve the same results. Take this simple example, as far as I understand both return exactly the same thing:

    SomeDataContext dc = new SomeDataContext();
    
    var queue = from q in dc.SomeTable
            where q.SomeDate &lt;= DateTime.Now &amp;&amp; q.Locked != true
            orderby (q.Priority, q.TimeCreated)
            select q;
    
    var queue2 = dc.SomeTable
            .Where( q =&gt; q.SomeDate &lt;= DateTime.Now &amp;&amp; q.Locked != true )
            .OrderBy(q =&gt; q.Priority)
            .ThenBy(q =&gt; q.TimeCreated);

The idea is that there are two ways to express the same thing; I understand that the first method has some limitations and that the &quot;dot notation&quot; is more complete, but besides that, are there any other advantages?

LINQ: Dot Notation vs Query Expression

I am working with a LINQ to SQL query and have run into an issue where I have 4 optional fields to filter the data result on.  By optional, I mean has the choice to enter a value or not.  Specifically, a few text boxes that could have a value or have an empty string and a few drop down lists that could have had a value selected or maybe not...

For example:

        using (TagsModelDataContext db = new TagsModelDataContext())
         {
            var query = from tags in db.TagsHeaders
                        where tags.CST.Equals(this.SelectedCust.CustCode.ToUpper()) 
                        &amp;&amp; Utility.GetDate(DateTime.Parse(this.txtOrderDateFrom.Text)) &lt;= tags.ORDDTE
                        &amp;&amp; Utility.GetDate(DateTime.Parse(this.txtOrderDateTo.Text)) &gt;= tags.ORDDTE
                        select tags;
            this.Results = query.ToADOTable(rec =&gt; new object[] { query });
        }
    
Now I need to add the following fields/filters, but only if they are supplied by the user.

 1. Product Number - Comes from another table that can be joined to TagsHeaders.
 2. PO Number - a field within the TagsHeaders table.
 3. Order Number - Similar to PO #, just different column.
 4. Product Status - If the user selected this from a drop down, need to apply selected value here.

The query I already have is working great, but to complete the function, need to be able to add these 4 other items in the where clause, just don&#39;t know how!

LINQ to SQL Where Clause Optional Criteria

I&#39;m currently brushing up on LINQ and am trying to comprehend the difference between the `let` and using the `into` keyword. So far the `let` keyword seems better than the `into` keyword as far as my understanding goes. 

The `into` keyword essentially allows one to continue a query after a projection. (Just want to state explicitly that I&#39;m not referring to the one for group join.)

Given an array of names it allows one to do the following:

    var intoQuery =
      from n in names
      select Regex.Replace(n, &quot;[aeiou]&quot;, &quot;&quot;)
      into noVowel
      where noVowel.Length &gt; 2
      select noVowel;

It takes the result of the select and places it into the `noVowel` variable which then allows one to introduce additional `where`, `orderby`, and `select` clauses. Once the `noVowel` variable is created, the `n` variable is no longer available. 

The `let` keyword, on the other hand, uses temp anonymous types to allow you to reuse more than one variable at a time. 

You can do the following:

    var letQuery =
      from n in names
      let noVowel = Regex.Replace(n, &quot;[aeiou]&quot;, &quot;&quot;)
      where noVowel.Length &gt; 2
      select noVowel;

Both the `noVowel` and `n` variables are available for use (even though I haven&#39;t used it in this case). 

While I can see the difference, I can&#39;t quite understand why one would want to use the `into` keyword over the `let` keyword unless one explicitly wanted to make sure that previous variables were not able to be used in latter parts of the query. 

So, is there a good reason why both keywords exist?

Is linq&#39;s let keyword better than its into keyword?

If I want to use objects as the keys for a `Dictionary`, what methods will I need to override to make them compare in a specific way?

Say I have a a class which has properties:

    class Foo {
        public string Name { get; set; }
        public int FooID { get; set; }

        // elided
    } 

And I want to create a:

    Dictionary&lt;Foo, List&lt;Stuff&gt;&gt;

I want `Foo` objects with the same `FooID` to be considered the same group.  Which methods will I need to override in the `Foo` class?

To summarize: I want to categorize `Stuff` objects into lists, grouped by `Foo` objects. `Stuff` objects will have a `FooID` to link them to their category.

Using the field of an object as a generic Dictionary key

I have a data structure which essentially amounts to a nested dictionary. Let&#39;s say it looks like this:

    
    {&#39;new jersey&#39;: {&#39;mercer county&#39;: {&#39;plumbers&#39;: 3,
                                      &#39;programmers&#39;: 81},
                    &#39;middlesex county&#39;: {&#39;programmers&#39;: 81,
                                         &#39;salesmen&#39;: 62}},
     &#39;new york&#39;: {&#39;queens county&#39;: {&#39;plumbers&#39;: 9,
                                    &#39;salesmen&#39;: 36}}}


Now, maintaining and creating this is pretty painful; every time I have a new state/county/profession I have to create the lower layer dictionaries via obnoxious try/catch blocks. Moreover, I have to create annoying nested iterators if I want to go over all the values. 

I could also use tuples as keys, like such:

    {(&#39;new jersey&#39;, &#39;mercer county&#39;, &#39;plumbers&#39;): 3,
     (&#39;new jersey&#39;, &#39;mercer county&#39;, &#39;programmers&#39;): 81,
     (&#39;new jersey&#39;, &#39;middlesex county&#39;, &#39;programmers&#39;): 81,
     (&#39;new jersey&#39;, &#39;middlesex county&#39;, &#39;salesmen&#39;): 62,
     (&#39;new york&#39;, &#39;queens county&#39;, &#39;plumbers&#39;): 9,
     (&#39;new york&#39;, &#39;queens county&#39;, &#39;salesmen&#39;): 36}

This makes iterating over the values very simple and natural, but it is more syntactically painful to do things like aggregations and looking at subsets of the dictionary (e.g. if I just want to go state-by-state).

Basically, sometimes I want to think of a nested dictionary as a flat dictionary, and sometimes I want to think of it indeed as a complex hierarchy. I could wrap this all in a class, but it seems like someone might have done this already. Alternatively, it seems like there might be some really elegant syntactical constructions to do this. 

How could I do this better?

Addendum: I&#39;m aware of `setdefault()` but it doesn&#39;t really make for clean syntax.  Also, each sub-dictionary you create still needs to have `setdefault()` manually set.

What is the best way to implement nested dictionaries?

I need to create an empty map.

    if (fileParameters == null)
        fileParameters = (HashMap&lt;String, String&gt;) Collections.EMPTY_MAP;

The problem is that the above code produces this warning: 
**Type safety: Unchecked cast from Map to HashMap&lt;String,String&gt;**

What is the best way to create this empty map?

Best way to create an empty map in Java

This is quite n00bish, but I&#39;m trying to learn/understand functional programming in python. The following code:

    foos = [1.0,2.0,3.0,4.0,5.0]
    bars = [1,2,3]
    
    def maptest(foo, bar):
        print foo, bar
    
    map(maptest, foos, bars)

produces:

    1.0 1
    2.0 2
    3.0 3
    4.0 None
    5.0 None

**Q. Is there a way to use map or any other functional tools in python to produce the following without loops etc.**

    1.0 [1,2,3]
    2.0 [1,2,3]
    3.0 [1,2,3]
    4.0 [1,2,3]
    5.0 [1,2,3]

**Just as a side note how would the implementation change if there is a dependency between foo and bar. e.g.**

    foos = [1.0,2.0,3.0,4.0,5.0]
    bars = [1,2,3,4,5]

**and print:**

    1.0 [2,3,4,5]
    2.0 [1,3,4,5]
    3.0 [1,2,4,5]
    ...

**P.S: I know how to do it naively using if, loops and/or generators, but I&#39;d like to learn how to achieve the same using functional tools. Is it just a case of adding an if statement to maptest or apply another filter map to bars internally within maptest?**

Using python map and other functional tools

If I have a dictionary like:

    {&#39;a&#39;: 1, &#39;b&#39;: 2, &#39;c&#39;: 3}

How can I convert it to this?

    [(&#39;a&#39;, 1), (&#39;b&#39;, 2), (&#39;c&#39;, 3)]

And how can I convert it to this?

    [(1, &#39;a&#39;), (2, &#39;b&#39;), (3, &#39;c&#39;)]

Content Type	Original Author	Original Content on Stackoverflow
Question	Scott Ivey	View Question on Stackoverflow
Solution 1 - C#	mmx	View Answer on Stackoverflow
Solution 2 - C#	leppie	View Answer on Stackoverflow

LINQ query to return a Dictionary<string, string>

C# Problem Overview

C# Solutions

Solution 1 - C#

Solution 2 - C#

Why can a function modify some arguments as perceived by the caller, but not others?

How to pipe list of files returned by find command to cat to view all the files

Attributions