Find Occurrence of a String

This article shows various ways to find the occurrence of a string in another string, or how to find a substring in a string. We are using the C# language to do this demo. At times, you may have encountered this requirement. This article is for those who don't know how to do this. We will be explaining two methods here. I hope you will like it.

Please see this article in my blog.

See demo.

Background

Today I got the requirement to create a function that does some operations depending on the occurrence of a string in a given string. Like, if a string pattern exists more than once in a given string, it must do some actions and if it occurs just once then it should do somethng else. I have done this in two ways, here I am sharing them. I hope you will find this useful.

Using the code

We will explain the following two ways to satisfy this requirement.

• Using Regex Class
• Using Custom Function

We will start with a Regex class first.

To start with Regex, you need to add another namespace as in the following:

Now consider we have designed our page as in the following code snippet:

And some CSS styles as follows.

If you add the preceding code and CSS, your page may look such as in the preceding image.



Now we will see our C# code. Please add the following lines of code on the button click event.

In the preceding code, we are finding the occurrence of a string using a Regex.Matches function. TheRegex.Matches function expects two parameters.

• Input String (the string to be searched)
• Pattern String (What we need to search for in the string)

We are getting those two values from our textarea and pass as follows.

Now if you run the application, you will get the following output:





As you can see I have given the words, “Sibeesh” and “passion” for testing and it gave the correct number of occurrences.

Now we will see how to do this using a Custom Function.

The following is our function call.

And here's the function body: