Windows set up project rollback

protected override void OnBeforeInstall(IDictionary savedState)
{
MessageBox.Show("OnBeforeInstall");
base.OnBeforeInstall(savedState);
error_msg = "";
try
{

string cd_key;
cd_key = Context.Parameters["PathValue"];
if (cd_key == "")
{
error_msg = "Enter Cd key to proceed further";
this.Rollback(savedState);
}
else
{
string str = "Select isnull(mac_id,'') as mac_id,cd_key,isnull(is_installed,0) as is_installed from tblInstallationMaster where cd_key='" + cd_key + "' and is_active=1";
try
{
ConnectionOpen();
}
catch (Exception ex)
{

error_msg = "You are not online. Net Connection problem";
this.Rollback(savedState);
}

if (string.IsNullOrEmpty(error_msg))
{
SqlCommand cmd = new SqlCommand(str, conn);

SqlDataReader dr = cmd.ExecuteReader();
bool has_rows = false;
string mac_id = "";
int is_installed = 1;
if (dr.HasRows)
{
dr.Read();
is_installed = int.Parse(dr["is_installed"].ToString());
mac_id = dr["mac_id"].ToString();
has_rows = true;
}
cmd = null;
ConnectionClose();
if (!has_rows)
{
error_msg = "Incorrect CD key";
this.Rollback(savedState);

}
else
{
if (string.IsNullOrEmpty(mac_id))
{

this.Install(savedState);

}
else if (mac_id == ConnectionClass.GetMACAddress())
{
// UpdateInstallationMaster();
if (is_installed == 0)
{
this.Install(savedState);

}
else
{

error_msg = "CD already Installed on your PC";
this.Rollback(savedState);

}

}
else
{
//MessageBox.Show("CD already Installed on " + mac_id);
error_msg = "CD already Installed on " + mac_id;
this.Rollback(savedState);

}
}
}
}
}
catch
{
MessageBox.Show(error_msg);
}
}
public override void Rollback(IDictionary savedState)
{ try
{
MessageBox.Show(error_msg);
base.Rollback(savedState);
}
catch
{
MessageBox.Show(error_msg);
}
}