Question

I just started work on a C# application. I need to break down a string into different parts. Is there an easy way to do this using C# patterns? I think I can do it with substrings but it might get messy and I want to do something that’s easy to understand. Here’s an example of the input:

AB-CDE-GHI-123-45-67-7777

variable1 = "AB-CDE-GHI"
variable2 = "123"
variable3 = "45"
variable4 = "67"
variable5 = "67-7777"

AB-CDE-GHIJKLM-123-45-67-7777

variable1 = "AB-CDE-GHIJKLM"
variable2 = "123"
variable3 = "45"
variable4 = "67"
variable5 = "67-7777"

AB-123-45-67-7777

variable1 = "AB"
variable2 = "123"
variable3 = "45"
variable4 = "67"
variable5 = "67-7777"

The first part of the string up until “123-45-67-7777” can be any length. Lucky for me the last part 123-45-67-7777 is always the same length and contains numbers that are zero padded.

I hope someone can come up with some suggestions for an easy method that uses regular expressions or something.

Input lines look like this:

aa-123-45-67-7777
HJHJH-123-45-67-7777
H-H-H--123-45-67-7777
222-123-45-67-7777

Answer 1

You do not need RegEx for parsing this kind of input.

You can use string.Split, in particular if the input is highly structured.

If you first split by - you will get a string[] with each part in a different index of the array.

The length property of the array will tell you how many parts you got and you can use that to reconstruct the parts you need.

You can rejoin any of the bit you need back.

string[] parts = "AB-CDE-GHI-123-45-67-7777".split('-');

// joining together the first 3 items:
string letters = string.Format("{0}-{1}-{2}", parts[0], parts[1], parts[2]);

// letters = "AB-CDE-GHI"

If the number of sections is variable (apart from the last 4), you can use the length in a loop to rebuild the wanted parts:

StringBuilder sb = new StringBuilder();
for(int i = 0; i < parts.Length - 4; i++)
{
  sb.FormatAppend("{0}-", parts[i]);
}
sb.Length = sb.Length - 1; // remove trailing -