Even if your issue is resolved, I'll try to clear out some things to you that you possibly don't know. Giving you a bunch of coding lines will only assist you temporarily.

Alright, maybe you aren't familiar that much with coding yet and Coding Enthusiast's scripts may be an overstatement to understand.

First off, it is required for you to know what's the background of a Bitcoin address, how it is structured etc. In this case, I'll explain you how a legacy address' structure, but it works similarly for Native SegWit and Nested SegWit. This bitcoin wiki article is useful. Briefly, a Bitcoin address is a base58 encoding of a string that contains these stuff in the following order: [version prefix][160-bit hash][checksum]

The checksum is the first four bytes of the prefix + 160-bit hash that is hashed two times with SHA256. For instance, if someone gave you this 160-bit hash:


You could get the checksum as following:


So, to be able to detect an address, you have to decode it and check if it has the above requirements; if the prefix along with the next 40 characters give you the same 4 bytes once hashed twice with SHA256, with the last 4 bytes of the decoded address. You can google for a base58 decoder script in C#, but it shouldn't be hard to write it yourself if you firstly understand how it works.

In Bitcoin, you should never hash a message as a text, but rather as a byte array.