how to perform join operations on sqlite.db for mobile app

iam new to xamarin 

i have developed a project in  xamarin.forms shared  project

 

in my project i have 2 data models

public class testing : IObject

{

public testing()

{

}

[PrimaryKey, AutoIncrement]

public int ID { get; set; }

[MaxLength(25)]

public string Names { get; set; }

[MaxLength(40)]

public string special{ get; set; }

[MaxLength(40)]

public string Username { get; set; }

[MaxLength(40)]

public string Email { get; set; }

[MaxLength(40)]

public int Phoneno { get; set; }

[MaxLength(20)]

public string Password { get; set; }

[MaxLength(30)]

public string Confirmpassword { get; set; }

[MaxLength(30)]

public string Address { get; set; }

}

public class model1 : IObject

{

public model1()

{

}

[PrimaryKey, AutoIncrement]

public int ID { get; set; }

[MaxLength(40)]

public int testingid { get; set; }

public string Name { get; set; }

[MaxLength(40)]

public string Username { get; set; }

[MaxLength(40)]

public string Password { get; set; }

[MaxLength(40)]

public string Confirmpassword { get; set; }

[MaxLength(40)]

public string Email { get; set; }

[MaxLength(20)]

public int Phoneno { get; set; }

[MaxLength(20)]

public string Address { get; set; }

 

here i object is an interface class

 

i want to join the  two tables for the purpose of   dispaly the special colume data by the name search criteria