find the first index of a substring in a string in csharp

To find the first index of a substring in a string in C#, you can use the IndexOf() method of the string class. The IndexOf() method takes a string parameter and returns the index of the first occurrence of the specified substring within the string. If the substring is not found, it returns -1.

Here's an example:

main.cs
string str = "The quick brown fox jumps over the lazy dog";
string substring = "fox";
int index = str.IndexOf(substring);

Console.WriteLine(index); // Outputs 16
163 chars
6 lines

In this example, we have a string str and a substring substring that we want to find the first index of within str. We call the IndexOf() method on str and pass in substring as a parameter. The method returns the index of the first occurrence of substring within str, which in this case is 16. We then output the result to the console.