asp.net membership change password without knowing old one

Evaluting the method signature, it is required to know old password while changing it.

membershipUser.ChangePassword(userWrapper.OldPassword, userWrapper.Password)

Is there any way to change password without knowing old one.

 string username = "username";
 string password = "newpassword";
 MembershipUser mu = Membership.GetUser(username);
 mu.ChangePassword(mu.ResetPassword(), password);

The other answers here are correct, but can leave the password in an unknown state.

ChangePassword will throw exceptions if the password doesn't meet the requirements laid out in Web.Config (minimum length, etc.). But it only fails after ResetPassword has been called, so the password will not be known to the original user or to the person who's tried to change it. Check for complexity requirements before changing the password to avoid this:

var user = Membership.GetUser(userName, false);

if ((newPassword.Length >= Membership.MinRequiredPasswordLength) &&
    (newPassword.ToCharArray().Count(c => !Char.IsLetterOrDigit(c)) >=
         Membership.MinRequiredNonAlphanumericCharacters) &&
    ((Membership.PasswordStrengthRegularExpression.Length == 0) ||
         Regex.IsMatch(newPassword, Membership.PasswordStrengthRegularExpression))) {

    user.ChangePassword(user.ResetPassword(), newPassword);
} else {
    // Tell user new password isn't strong enough
}

You need to reset the user's password before changing it, and pass in the generated password to ChangePassword.

string randompassword = membershipUser.ResetPassword();
membershipUser.ChangePassword(randompassword , userWrapper.Password)

or inline:

membershipUser.ChangePassword(membershipUser.ResetPassword(), userWrapper.Password)

Try to use SimpleMembershipProvider it's easier:

var token = WebSecurity.GeneratePasswordResetToken("LoginOfUserToChange");
WebSecurity.ResetPassword(token, "YourNewPassword");

Please note, all these mentioned solutions will only work if the RequiresQuestionAndAnswer property is set to false in Membership system configuration. If RequiresQuestionAndAnswer is true then the ResetPassword method needs to be passed the security answer, otherwise it will throw an exception.

In case you need RequiresQuestionAndAnswer set to true, you can use this workaround

This code mentioned on posts above is working:

string username = "username";
string password = "newpassword";
MembershipUser mu = Membership.GetUser(username);
mu.ChangePassword(mu.ResetPassword(), password);

But you have to set requiresQuestionAndAnswer="false" in web.config in membership provider tag. If it is true, resetpassword method generate an error "Value can not be null". In this case you must supply question answer as parameter to ResetPassword.

Use the password you want to set from textbox in place of 123456.

 MembershipUser user;     
 user = Membership.GetUser(userName,false);
 user.ChangePassword(user.ResetPassword(),"123456");

@Rob Church is right:

> The other answers here are correct but can leave the password in an > unknown state.

However, instead of his solution to do the validation by hand, I would try to change the password using the ResetPassword from token method and catch and show the error:

var user = UserManager.FindByName(User.Identity.Name);
string token = UserManager.GeneratePasswordResetToken(user.Id);
var result = UserManager.ResetPassword(user.Id, token, model.Password);
if (!result.Succeeded){
    // show error
}

string username = "UserName";
string userpassword = "NewPassword";
string resetpassword;
    
MembershipUser mu = Membership.GetUser(username, false);

if (mu == null){
    Response.Write("<script>alert('Invalid Username!')</script>"); 
}

else{
    resetpassword = mu.ResetPassword(username);
    if (resetpassword != null){
         if (mu.ChangePassword(resetpassword, userpassword)){
             Response.Write("<script>alert('Password changed successfully!')</script>"); 
         }
    }
    else{
           Response.Write("<script>alert('Oh some error occurred!')</script>"); 
        }
    }

 string username = "UserName";
 string userpassword = "NewPassword";   
 MembershipUser mu = Membership.GetUser(username, false);
 mu.ChangePassword(mu.ResetPassword(username), userpassword);