C # is inaccessible due to its level of protection and can only handle detailed code descriptions of public types

Encountered an error in implementing C # exporting the list data to an XML file [with Source]: not accessible because of its level of protection. Only public types can be processed.

The line of code that generated the error:

XmlSerializer XmlSerializer = new XmlSerializer (typeof (List<usermodel>));

Reason for error: class definition in the following code is:

Class Usermodel

No public access modifier added

    <summary>///User entity class//////////////////////////NOTE: The class must have the access modifier: public, otherwise an error occurs:    Only public types can be processed.        </summary> [Serializable] public class Usermodel {private Long id = 1;        private string name = "Name";        private int gender = 0;        private int age = 20;        private string userName = "UserName";        private string password = "password";            Public long ID {get {return Id;}        set {id = value;}            } public string Name {get {return Name;}        set {name = value;}            } public int Gender {get {return Gender;}        set {gender = value;}            } public int Age {get {return-age;}        set {age = value;}            } public string UserName {get {return UserName;}        set {userName = value;} } public string Password {get { return password;        } set {password = value;} }    }