Merging IEnumerable Sequences in C# with LINQ

The Zip method allows us to join IEnumerable sequences together by interleaving the elements in the sequences.

Zip is an extension method on IEnumerable. For example to zip together a collection of names with ages we could write:

var names = new [] {"John", "Sarah", "Amrit"};

var ages = new[] {22, 58, 36};

var namesAndAges = names.Zip(ages, (name, age) => name + " " + age);    

This would produce an IEnumerable<string> containing three elements:

  • “John 22”
  • “Sarah 58”
  • “Amrit 36”

If one sequence is shorter that the other, the “zipping” will stop when the end of the shorter sequence is reached. So if we added an extra name:

var names = new [] {"John", "Sarah", "Amrit", "Bob"};

We’d end up with the same result as before, “Bob” wouldn’t be used as there isn’t a corresponding age for him.

We can also create objects in our lambda, this example shows how to create an IEnumerable of two-element Tuples:

var names = new [] {"John", "Sarah", "Amrit"};

var ages = new[] {22, 58, 36};

var namesAndAges = names.Zip(ages, (name, age) => Tuple.Create(name, age)); 

This will produce an IEnumerable<Tuple<String,Int32>> that contains three Tuples, with each Tuple holding a name and age.


(The .Zip method is one of a smorgasbord of C# Tips and Traps that I cover in my Pluralisight C# courses.)

Auto-Generating Sequences of Integer Values in C#

When we need to generate a sequence of integer values, we can do it manually using some kind of loop, or we make use of the Enumerable.Range method.

The following code illustrates:

var oneToTen = Enumerable.Range(1, 10);

int[] twentyToThirty = Enumerable.Range(20, 11).ToArray();

List<int> oneHundredToOneThirty = Enumerable.Range(100, 31).ToList();

We can also use the results of .Range and transform them in some way, for example to get the letters of the alphabet we could write something like this:

var alphabet = Enumerable.Range(0, 26).Select(i => Convert.ToChar('A' + i));

This will generate an IEnumerable<char> containing the letters A through Z.


(The .Range method is one of a smorgasbord of C# Tips and Traps that I cover in my Pluralisight C# courses.)

Automated Acceptance Testing with SpecFlow and Gherkin Course

With my new Pluralsight course you’ll learn how to narrow the gap between the business/customer and the development team by creating business-readable, automated tests.

The course covers how to install SpecFlow in Visual Studio, the Gherkin business-readable domain specific language (DSL), and how to create code-automation from this natural language.

You can find the course on my Pluralsight author page.

Creating Inline Data Driven Tests in xUnit allows the creation of data-driven tests. These kind of tests get their test data from outside the test method code via parameters added to the test method signature.

Say we had to test a Calculator class and check it’s add method returned the correct results for six different test cases. Without data-driven tests we’d either have to write six separates tests (with almost identical code) or some loop inside our test method containing an assert.

Regular test methods are identified by applying the [Fact] attribute. Data-driven tests instead use the [Theory] attribute.

To get data-driven features and the [Theory] attribute, install the Extensions NuGet package in addition to the standard package.

Creating Inline Data-Driven Tests

The [InlineData] attribute allows us to specify test data that gets passed to the parameters of test method.

So for our Calculator add test we’d start by defining the test method:


Improving Struct Equality Performance in C#

The equality performance of struct equality comparisons can be improved by overriding .Equals(). This is especially true if the structs we are comparing contain reference type fields.

By default, the equality of structs is automatically determined by doing a byte-by-byte comparison of the two struct objects in memory – only when the structs don’t contain any reference types. When the structs contain reference type fields then reflection is used to compare the fields of the two struct objects which results in slower performance.

This chart show the relative performance of the default equality of a struct that contains only value types against a struct that also contains a reference type:

struct equality performance chart


New Pluralsight Course: The Testing Framework

My latest Pluralsight course on the testing framework has just been released.

Course Description

Learn the latest in unit testing technology for C#, VB.NET (and other .NET languages) created by the original inventor of NUnit. is a free, extensible, open source framework designed for programmers that aligns more closely with the .NET platform.


You can check it out now on

You Don’t Have to Write a Generic Class to Use Generic Methods in C#

We can create generic classes such as:

class ThingWriter<T>
    public void Write(T thing)

Here we’re defining a generic class, then using the type T as a method parameter in the Write method. To use this class we’d write something like:

var w = new ThingWriter<int>();


We don’t however have to be working in a generic class to make use of generic methods.


Converting Chars to Doubles in C#

If we’ve got chars with numeric digits in them, we can convert them to numeric (double) values using the char.GetNumericValue method.

The following code:

double d = char.GetNumericValue('5');


Outputs the value: 5

So why does GetNumericValue return a double when a char can only be a single character and hold a single “number” (‘0’ to ‘9’)? Because char holds Unicode characters.

So the following code:

double d = char.GetNumericValue('⅔');


Outputs the value: 0.666666666666667

Hence the need for GetNumericValue to return a double.


For more C# tips check out my Pluralsight courses: C# Tips and Traps and C# Tips and Traps 2.

What’s the Difference Between & and && in C# ?

My previous article “Non Short Circuiting C# Conditional Operators” garnered some comments which suggested to me that I should expand on it. There can sometimes be some confusion over the & and && operator in C# so hopefully this article goes some way to helping clarify the differences between them.

The && Operator

Works with: bools

The && operator performs a logical AND on Boolean values.

For example, the following code:

bool b1 = true;
bool b2 = false;

bool isBothTrue = b1 && b2;




If we get our two bool values from the result of a couple of methods instead, and the first method returns false, the && operator won’t execute the second method. The following code: