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Using ConvertAll to Convert a Set of Values

ConvertAll is one of those methods that is not used very often, but when you need it, it is very useful. It converts all of the elements of one list or array into element of another type. In this example the user enters a list of numbers into a TextBox as a string, that list is converted to a list of...

Posted to Deborah's Developer MindScape by Deborah Kurata on Wed, Dec 1 2010
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda
Associating Code with a Tag using Delegates II

This prior post demonstrated how to use delegates to associated code with a Tag in a WinForms control. This post shows how to accomplish the same thing using Lambda expressions to define the delegate. To try out this example, create a WinForms application and add a TreeView control to the form. Then...

Posted to Deborah's Developer MindScape by Deborah Kurata on Fri, Nov 19 2010
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda, WinForms, Delegate
SelectMany: Finding in a Child List

In this prior post , I demonstrated how to find a specific item in a generic list of items. But what if the item you want to find is in a child list? For example, a list of customers where each customer is a company that has a company name and a list of contact persons. You may want to find a customer...

Posted to Deborah's Developer MindScape by Deborah Kurata on Sat, Oct 30 2010
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda
Sorting Lists with Null Values

When working with data, you often have values that are null. For example, you may allow entry of a user's birthday, but not require entry. So some of your rows may contain a null date. Or your application may track a customer's last order date, which will be null if you track potential customers...

Posted to Deborah's Developer MindScape by Deborah Kurata on Sat, Oct 30 2010
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda, WinForms
LINQ: Mean, Median, and Mode

If you are doing any type of statistical analysis, you probably need to calculate mean, median and mode. There are lots of places on the Web you can find the calculations. This post is different than most in that it uses LINQ and Lambda expressions. Mean is the statistical average of a set of numbers...

Posted to Deborah's Developer MindScape by Deborah Kurata on Fri, May 7 2010
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda, LINQ
Multi-dimensional Arrays and IEnumerable

Most of the cool extension methods that you can use with Lambda expressions, such as Where, FirstOrDefault, and Zip, are extensions of the generic IEnumerable<T> class. Interestingly, the .NET multi-dimensional array does not implement the generic IEnumerable<T> class. So you don't have...

Posted to Deborah's Developer MindScape by Deborah Kurata on Wed, May 5 2010
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda
Lambda Expressions: Zip

One of the new features in C# 4 and VB 10 (.NET 4.0) is the Zip extension method on IEnumerable. This method allows you to merge two lists such as two arrays or two generic List<T>. The Zip extension method merges the two sequences by matching up each item in one sequence with another item in another...

Posted to Deborah's Developer MindScape by Deborah Kurata on Tue, May 4 2010
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda
Grouping and Summing with Lambda Expressions

There are often cases where you need to group on multiple properties and potentially sum on others. This post details how to group and sum on multiple properties using lambda expressions. This example uses an Invoice class, since that provides many opportunities for summing. First, here is a basic Invoice...

Posted to Deborah's Developer MindScape by Deborah Kurata on Tue, May 4 2010
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda, LINQ
Generating Random Letters

Someone recently posted in the forums the need to build a " Word Search " puzzle and wanted to generate a list of random letters. .NET has all of the features you need to do this in just two lines of code. In C#: Random rand = new Random(); var letter = Enumerable.Range(0, 100).Select...

Posted to Deborah's Developer MindScape by Deborah Kurata on Tue, Mar 30 2010
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda
Lambda Expressions: Join

If you have a set of business objects that are related to another set of business objects by a foreign key, you can use the Join method in a Lambda expression to join the two sets of business objects into one. You can then use the resulting set as a single list. This is useful when you need to perform...

Posted to Deborah's Developer MindScape by Deborah Kurata on Wed, Mar 3 2010
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda
Binding to a ComboBox using a DataTable and Linq

If you retrieve data into a DataTable, it is easy to bind it to a ComboBox. And before Linq, you would filter the DataTable using a DataView. But with Linq, you have some easy to use features for filtering the contents of your ComboBox. First, here is the basic code for binding a ComboBox to a DataTable...

Posted to Deborah's Developer MindScape by Deborah Kurata on Sat, Feb 27 2010
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda, LINQ, DataTable, Binding
Finding a Node in an XML String

A common requirement with an XML file is to find a particular node. If you are targeting the .NET framework 3.5 or higher, you can find the node using Linq to XML or by using Lambda expressions. As with many of my prior XML examples, the XML string is as follows: <States> <State name...

Posted to Deborah's Developer MindScape by Deborah Kurata on Sun, Jan 31 2010
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda, Xml, LINQ
Lambda Expressions: Execution

Lambda expressions can be assigned to a delegate variable. The lambda expression is then executed when the delegate is called. [To begin with an overview of lambda expressions, start here .] In the following example, a lambda expression is assigned to a variable (f). In C#: Func<int,string> f ...

Posted to Deborah's Developer MindScape by Deborah Kurata on Fri, Oct 16 2009
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda, Delegate
Lambda Expressions: Func Delegates

A Func delegate encapsulates a method that returns a value. It takes up to four parameters (and this number is increased in .NET 4.0) plus the return value. [To begin with an overview of lambda expressions, start here .] The following signature is a Func delegate that takes two integer parameters and...

Posted to Deborah's Developer MindScape by Deborah Kurata on Sun, Oct 11 2009
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda, Delegate
Lambda Expressions: Action Delegates

Just as the name implies, an action delegate encapsulates a method that performs an action and has no return value. It takes up to four parameters (and this number is increased in .NET 4.0). [To begin with an overview of lambda expressions, start here .] The ForEach method of the List<T> is an...

Posted to Deborah's Developer MindScape by Deborah Kurata on Sun, Oct 11 2009
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda, Delegate
Lambda Expressions: Predicate Delegates

According to Wikipedia , a predicate is “a function which returns a Boolean value”. [To begin with an overview of lambda expressions, start here .] A predicate delegate encapsulates a method that evaluates to True or False. It takes a single parameter. The Array class Find method is an example of a predicate...

Posted to Deborah's Developer MindScape by Deborah Kurata on Sun, Oct 11 2009
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda, Delegate
Lambda Expressions: Syntax

This post covers the syntax for lambda expressions. It uses the customer list defined in this prior post . [To begin with an overview of lambda expressions, start here .] The first example below uses the FirstOrDefault extension method on the Enumerable object to find the first customer that matches...

Posted to Deborah's Developer MindScape by Deborah Kurata on Sun, Oct 11 2009
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda
Delegates

A delegate is an object that holds a reference to a method with a particular parameter list and return type. It is basically like an object-oriented, type-safe function pointer. Delegates basically make it possible to treat methods as entities. You can then assign a delegate to a variable or pass it...

Posted to Deborah's Developer MindScape by Deborah Kurata on Sun, Oct 11 2009
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda, Delegate
Lambda Expressions: Finding an Item in a Generic List

In this prior post , I detailed how to build lists of things using a generic List<T>. Once you have a list, you may need to find items in the list. There are several ways to accomplish this, but using lambda expressions is the most concise. [To begin with an overview of lambda expressions, start...

Posted to Deborah's Developer MindScape by Deborah Kurata on Sun, Oct 11 2009
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda, LINQ, Generics
Lambda Expressions: An Introduction

My presentation at our local Code Camp was fun. I covered a lot of material and had a GREAT audience. Several people have asked for the slide information in my blog. So this is the start of several posts on lambda expressions. In addition, I wrote an article on lambda expressions that should appear in...

Posted to Deborah's Developer MindScape by Deborah Kurata on Sun, Oct 11 2009
Filed under: Filed under: VB, C#, .NET, CSharp, Lambda, Generics, Delegate

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