Wp7 Bind data from Global class

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C#

Hello All,
May be this is very simple but I am not able to get it. I have simple Common class as below

namespace Project.source
{
  class GlobalClass
        {
            public int TextBoxSize { get {return 30;}}
            public int TextMaxWidth {get {return 50;}}
            //it continues .... 
        }
}

Now in mainPage.xaml I need to bind it to my TextBox

<TextBox Name="txtInput"  FontSize="{binding ?????????}" width="{binding ????}" />

Also Please note that namespace of mainPage.xaml is only Project
How can I Bind textbox from other class ?