Rather than using side-effects, use the overload of `Select` which takes an index:

    stuff.Select((value, index) =&gt; new { index, value.Name });

You *could* do it using side-effects, but not in the way you tried:

    int counter = 0;
    var query = from a in stuff
                select new { count = counter++, a.Name };

I would strongly advise against this though.

If you truly want it to be a counter, and not just an index, then just move the counter declaration outside the LINQ expression

    var counter = 0;
    from a in stuff
    select new { count = counter++; a.Name };

Just add two variable here `NumberRow` is for that

```
.Select((x,NumberRow) =&gt; new ViewModelArchiveOrder
                    {
                        NumberRow= NumberRow + 1,
                    })
```

Case
----------
Normally you would use the `cellForRowAtIndexPath` delegate method to setup your cell. The information set for the cell is important for how the cell is drawn and what the size will be.

Unfortunatly the `heightForRowAtIndexPath` delegate method is called before the `cellForRowAtIndexPath` delegate method so we can&#39;t simply tell the delegate to return the height of the cell, since this will be zero at that time.

So we need to calculate the size before the cell is drawn in the table. Luckily there is a method that does just that, `sizeWithFont`, which belongs to the NSString class. However there is problem, in order to calculate the correct size dynamically it needs to know how the elements in the cell will be presented. I will make this clear in an example:

Imagine a `UITableViewCell`, which contains a label named `textLabel`. Within the `cellForRowAtIndexPath` delegate method we place `textLabel.numberOfLines = 0`, which basically tells the label it can have as many lines as it needs to present the text for a specific width. The problem occurs if we give textLabel a text larger then the width originally given to textLabel. The second line will appear, but the height of the cell will not be automatically adjusted and so we get a messed up looking table view.

As said earlier, we can use `sizeWithFont` to calculate the height, but it needs to know which Font is used, for what width, etc. If, for simplicity reasons, we just care about the width, we could hardcode that the width would be around 320.0 (not taking padding in consideration). But what would happen if we used UITableViewStyleGrouped instead of plain the width would then be around 300.0 and the cell would again be messed up. Or what happends if we swap from portrait to landscape, we have much more space, yet it won&#39;t be used since we hardcoded 300.0.

This is the case in which at some point you have to ask yourself the question how much can you avoid hardcoding.


My Own Thoughts
----------
You could call the `cellForRowAtIndexPath` method that belongs to the UITableView class to get the cell for a certain section and row. I read a couple of posts that said you don&#39;t want to do that, but I don&#39;t really understand that. Yes, I agree it will already allocate the cell, but the `heightForRowAtIndexPath` delegate method is only called for the cells that will be visible so the cell will be allocated anyway. If you properly use the `dequeueReusableCellWithIdentifier` the cell will not be allocated again in the `cellForRowAtIndexPath` method, instead a pointer is used and the properties are just adjusted. Then what&#39;s the problem? 

Note that the cell is NOT drawn within the `cellForRowAtIndexPath` delegate method, when the table view cell becomes visible the script will call the `setNeedDisplay` method on the UITableVieCell which triggers the `drawRect` method to draw the cell. So calling the `cellForRowAtIndexPath` delegate directly will not lose performance because it needs to be drawn twice.

Okay so by calling the `cellForRowAtIndexPath` delegate method within the `heightForRowAtIndexPath` delegate method we receive all the information we need about the cell to determine it&#39;s size. 

Perhaps you can create your own `sizeForCell` method that runs through all the options, what if the cell is in Value1 style, or Value2, etc.

Conclusion/Question
----------
It&#39;s just a theory I described in my thoughts, I would like to know if what I wrote is correct. Or that maybe there is another way to accomplish the same thing. Note that I want to be able to do things as flexible as possible.

UITableView flexible/dynamic heightForRowAtIndexPath

I am trying to produce a simple scripting system that will be used to print labels. I have done this in the past with reflection with no problem, but I am now trying to do it with Lambda functions so that I can cache the functions for reuse.

The code I have so far is as follows...

    public static string GetValue&lt;T&gt;(T source, string propertyPath) {
    
    	try {
    
    		Func&lt;T, Object&gt; func;
    
    		Type type = typeof(T);
    		ParameterExpression parameterExpression = Expression.Parameter(type, @&quot;source&quot;);
    		Expression expression = parameterExpression;
    		foreach (string property in propertyPath.Split(&#39;.&#39;)) {
    			PropertyInfo propertyInfo = type.GetProperty(property);
    			expression = Expression.Property(expression, propertyInfo);
    			type = propertyInfo.PropertyType;
    		}
    
    		func = Expression.Lambda&lt;Func&lt;T, Object&gt;&gt;(expression, parameterExpression).Compile();
    
    		object value = func.Invoke(source);
    		if (value == null)
    			return string.Empty;
    		return value.ToString();
    
    	}
    	catch {
    
    		return propertyPath;
    
    	}
    
    }

This seems to work in some cases, but in others it fails. The problem seems to be in my trying to return the values as objects - irrespective of the actual data types. I am trying to do this because I do not know at compile time what the data type will be but in the long run, I only need a string.

I am getting the exception shown in the title of this message whenever I try to access a property of type Int32 - but I am also getting it for Nullable&lt;DateTime&gt; types and others.
 The exception is thrown when I try to compile the expression into the function.

Can anybody suggest how I might go about this differently whilst maintaining the Lambda functionality so that I can cache the accessors?


Expression of type &#39;System.Int32&#39; cannot be used for return type &#39;System.Object&#39;

I want to do something like this:

    from a in stuff
    let counter = 0
    select new { count = counter++, a.Name };

But I get a error telling me that counter is read only. Is there a way to do something similar to this, without declaring a variable outside of the query?

Basically, I just want to show a count/index column in [LINQPad][1] (which is awesome, BTW), which means I can&#39;t declare counter ahead of time.


  [1]: http://www.linqpad.net/

Can I have an incrementing count variable in LINQ?

I want to do something like this:
<pre><code class="hljs language-ini">from a in stuff
let counter = 0
select new { count = counter++, a.Name };
</code></pre>
But I get a error telling me that counter is read only. Is there a way to do something similar to this, without declaring a variable outside of the query?
Basically, I just want to show a count/index column in <a href="http://www.linqpad.net/" target="_blank" rel="noopener noreferrer">LINQPad</a> (which is awesome, BTW), which means I can't declare counter ahead of time.

I&#39;m trying to get my linq statement to get me all records between two dates, and I&#39;m not quite sure what I need to change to get it to work: `(a.Start &gt;= startDate &amp;&amp; endDate)`

    var appointmentNoShow =
        from a in appointments
        from p in properties
        from c in clients
        where a.Id == p.OID &amp;&amp; (a.Start.Date &gt;= startDate.Date &amp;&amp; endDate)

C# Linq Where Date Between 2 Dates

Does LINQ model the aggregate SQL function `STDDEV()`  (standard deviation)?

If not, what is the simplest / best-practices way to calculate it?

Example:

      SELECT test_id, AVERAGE(result) avg, STDDEV(result) std 
        FROM tests
    GROUP BY test_id

Standard Deviation in LINQ

I start with a basic class that I want to manipulate in a List using LINQ, something like the following:

    public class FooBar   
    {  
        public virtual int Id { get; set; }  
        public virtual string Foo { get; set; }  
        public virtual string Bar { get; set; }
    }

This is what I ultimately found out to solve my problem using the non lambda LINQ stuff.

    // code somewhere else that works and gets the desired results  
    var foobarList = GetFooBarList();  // Abstracted out - returns List&lt;Foobar&gt;  

    // Interesting piece of code that I want to examine
    var resultSet = from foobars in foobarList  
                    orderby foobars.Foo, foobars.Bar  
                    select foobars;

    // Iterate and do something interesting  
    foreach (var foobar in resultSet)  
    {  
        // Do some code  
    }

What I&#39;m really curious about is if the same can be accomplished using the Lambda based extension methods off of generic `IEnumerable` to accomplish the same thing.  Google tells me I can do something like the following to accomplish it:

    var resultSet = foobarList.OrderBy(x =&gt; new {x.Foo, x.Bar})  
                              .Select(x=&gt;x);

However if I do that I get a runtime error when I hit the `foreach` statement.  The error tells me that at least one object has to implement `IComparible`, which I can see that since I&#39;m using an anonymous type for the `.OrderBy()` method.

So is there a way to accomplish what I want using the Lambda way?


Multiple Order By with LINQ

With linq I have to check if a value of a row is present in an array.  
The equivalent of the sql query:

    WHERE ID IN (2,3,4,5)

How can I do it?

What is the linq equivalent to the SQL IN operator

How would you implement paging in a LINQ query? 
Actually for the time being, I would be satisfied if the sql TOP function could be imitated. However, I am sure that the need for full paging support comes up sooner later anyway.

    var queryResult = from o in objects
                      where ...
                      select new
                          {
                             A = o.a,
                             B = o.b
                          }
                       ????????? TOP 10????????



Paging with LINQ for objects

LINQPad is amazing, and particularly useful is the `Dump()` extension methods which renders objects and structs of almost any type, anonymous or not, to the console.

Initially, when I moved to Visual Studio 2010, I tried to make my own `Dump` method using a delegate to get the values to render for anonymous types, etc. It&#39;s getting pretty complicated though and while it was fun and educational at first, I need a solid implementation. Having checked out the LINQPad code in [.NET Reflector][1] I am even more assured that I&#39;m not going to get the implementation right.

Is there a free library I can include to provide the `Dump` functionality?


  [1]: http://en.wikipedia.org/wiki/.NET_Reflector

How do I use the LINQPad Dump() extension method in Visual Studio?

&lt;!-- language-all: lang-cs --&gt;
&lt;!-- For available tags, see: http://pastebin.com/AWMtu5rK --&gt;
&lt;!-- and: http://meta.stackexchange.com/questions/72082/changes-to-syntax-highlighting --&gt;
Does anyone have a complete list of LINQPad extension methods and methods, such as

    .Dump()

    SubmitChanges()

LINQPad [extension] methods

Does anyone know how to get hold of the path to the directory where the LINQPad script file (.linq) resides?

Or to the script itself for that matter.

Note that I&#39;m not talking about the location of the &quot;My Queries&quot; folder, the one shown inside LINQPad.

I can save a .linq file anywhere on disk, and open it by double-clicking on it.

For instance, if I save the file to `C:\Temp\Test.linq`, and execute the program, I&#39;d like to have either `C:\Temp` or `C:\Temp\Test.linq`.

Basically I&#39;d like something akin to `Environment.CurrentDirectory` or `Assembly.GetEntryAssembly().Location`, just for the .linq file.

Things I&#39;ve tried:

* Looking through environment variables
* Looking through the LINQPad assembly that is given to my script
* Throwing an exception and looking at the stacktrace (contains a link to a temporary copy of my script somewhere else)
* `Environment.CommandLine.Dump();` - gives LINQPad executable
* `Environment.CurrentDirectory.Dump();` - gives C:\windows\system32
* `Assembly.GetExecutingAssembly().Location.Dump();` - gives temp directory

LINQPad script directory?

I&#39;ve found LINQPad to be extremely useful when answering StackOverflow questions for C# or VB.NET. It allows me to write up some quick code, run it, and (if I want) see a nicely-formatted dump of the results. That way I can be sure that the code I post actually runs. Thus far I haven&#39;t seen anything that I can use to achieve the same result with Java. Is there anything like that out there?

*I am **not** looking for something to query data sources*; I just want a light-weight IDE. These are the features I&#39;m particularly interested in:

 - The ability to write and run short snippets of code without establishing a whole project or file structure.
 - Reporting of compiler and runtime errors in the code when it is run.
 - The ability to add references to a particular editor instance.
 - Syntax highlighting and Autocomplete/Intellisense would be a plus.

Is there any program like LINQPad for Java?

Using LINQPad, using the extension method Dump(), Console.WriteLine or Debug.Writeline, the values will appear in the results window.

Is there a way to clear this results window during the run of a linqpad script?  As an example, I tried Console.Clear() however this throws an exception

Content Type	Original Author	Original Content on Stackoverflow
Question	Mike Pateras	View Question on Stackoverflow
Solution 1 - Linq	Jon Skeet	View Answer on Stackoverflow
Solution 2 - Linq	JaredPar	View Answer on Stackoverflow
Solution 3 - Linq	saeed bagheri	View Answer on Stackoverflow

Can I have an incrementing count variable in LINQ?

Linq Problem Overview

Linq Solutions

Solution 1 - Linq

Solution 2 - Linq

Solution 3 - Linq

Expression of type 'System.Int32' cannot be used for return type 'System.Object'

UITableView flexible/dynamic heightForRowAtIndexPath

Attributions