Hi SUJAYS,
Check this example. Now please take its reference and correct your code.
Code
C#
protected void Page_Load(object sender, EventArgs e)
{
    string varialble = "aspsnippets.com";
    ClassA a = new ClassA();
    string message = a.Test1(varialble);
    ClassB b = new ClassB();
    string output = b.Test2(message);
    Response.Write(string.Format("Welcome message from ClassB is <b>{0}</b>", output));
}
public interface Test
{
    string Test1(string a);
    string Test2(string a);
}
public class ClassA : Test
{
    public string Test1(string a)
    {
        return a;
    }
    public string Test2(string a)
    {
        return a;
    }
}
public class ClassB : Test
{
    public string Test1(string a)
    {
        return a;
    }
    public string Test2(string a)
    {
        return a;
    }
}
VB.Net
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    Dim varialble As String = "aspsnippets.com"
    Dim a As ClassA = New ClassA()
    Dim message As String = a.Test1(varialble)
    Dim b As ClassB = New ClassB()
    Dim output As String = b.Test2(message)
    Response.Write(String.Format("Welcome message from ClassB is <b>{0}</b>", output))
End Sub
Public Interface Test
    Function Test1(ByVal a As String) As String
    Function Test2(ByVal a As String) As String
End Interface
Public Class ClassA
    Implements Test
    Public Function Test1(ByVal a As String) As String Implements Test.Test1
        Return a
    End Function
    Public Function Test2(ByVal a As String) As String Implements Test.Test2
        Return a
    End Function
End Class
Public Class ClassB
    Implements Test
    Public Function Test1(ByVal a As String) As String Implements Test.Test1
        Return a
    End Function
    Public Function Test2(ByVal a As String) As String Implements Test.Test2
        Return a
    End Function
End Class
Output
Welcome message from ClassB is aspsnippets.com