How do I calculate the equivalent to SQL Server (hashbytes('SHA1',[ColumnName])) in C#?

Question

In my database I have a computed column that contains a SHA1 hash of a column called URLString which holds URLs (e.g. \"http://xxxx.com/index.html\").

I often need t

Answer 1

Below are two methods that do hashing of string and of bytes. The HashBytes method returns Base64 of the resulting bytes but you can return just the bytes if you prefer them

public static string HashString(string cleartext)
{
    byte[] clearBytes = Encoding.UTF8.GetBytes(cleartext);
    return HashBytes(clearBytes);
}  

public static string HashBytes(byte[] clearBytes)
{
    SHA1 hasher = SHA1.Create();
    byte[] hashBytes =   hasher.ComputeHash(clearBytes);
    string hash = System.Convert.ToBase64String(hashBytes);
    hasher.Clear();
    return hash;
}