here we need to add the SharpSvn Api dll reference into c# project. link for SharpSvn package download and then follow the below link for example code for getting top revision number
SvnInfoEventArgs statuses;
SvnClient client = new SvnClient();
client.Authentication.Clear();//clear a previous authentication
client.Authentication.DefaultCredentials =
new System.Net.NetworkCredential("usr", "pass");
client.GetInfo("svn://india00/Repo/branches/xyz", out statuses);
int LastRevision = (int)statuses.LastChangeRevision;`
add references as
using SharpSvn;
using System.Collections.Generic;
using System.Collections.ObjectModel;`