System.Environment of mscorlib assembly helps you to fetch the server list as:
using System.Environment;
string myServer = Environment.MachineName;
DataTable servers = SqlDataSourceEnumerator.Instance.GetDataSources();
for (int i = 0; i < servers.Rows.Count; i++)
{
if (myServer == servers.RowsIdea["ServerName"].ToString()) {
if ((servers.RowsIdea["InstanceName"] as string) != null)
CmbServerName.Items.Add(servers.RowsIdea["ServerName"] + "\\" + servers.RowsIdea["InstanceName"]);
else
CmbServerName.Items.Add(servers.RowsIdea["ServerName"]);
}
}