Enumerate over all available SQL Server instances.

EnumerateSqlServers.cs

DataTable data = SqlDataSourceEnumerator.Instance.GetDataSources();
foreach(DataRow row in data.Rows) {
    string server = row["ServerName"].ToString();
	string instance = row["InstanceName"].ToString();
	if (!string.IsNullOrWhiteSpace(instance)) {
		server += "\\" + instance;
	}
	
	Console.WriteLine(server);
}