how to set and get value of privae members of inheritence

When you declare them as private, they can only be accessed from within that class, and no other:

public class MyBase
    {
    private string MyProp { get; set; }
    public void Method(string s) { MyProp = s; }
    public string OtherMethod() { return MyProp; }
    }
public class MyDerived : MyBase
    {
    public void SetIt()
        {
        MyProp = "hello";  // **** ERROR ****
        Method("Hello");   // OK
        }
    }

Even if you derive a new class from MyBase, the new class cannot access the private members. To allow that, you can declare it as protected:

{
    protected string MyProp { get; set; }
    public void Method(string s) { MyProp = s; }
    public string OtherMethod() { return MyProp; }
    }
public class MyDerived : MyBase
    {
    public void SetIt()
        {
        MyProp = "hello";   // OK
        Method("Hello");    // OK
        }
    }

Anything declared within a class is available anywhere within that class regardless of the protection level, but you can restrict access to it outside the class, using the private, protected and internal specifiers.