How to check Password exist in Membership Table ?

Ø     Hi

               How to check password exists in asp.net Membership Table? Or How to check old password and new password.

          Ex:

                                  object objUserID = (System.Guid)Membership.GetUser(strEmployerUserName).ProviderUserKey;

                            MembershipUser objUsr = Membership.GetUser(objUserID);

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