Convert 1011₂ to base 10.

1 x 2⁰ = 1
1 x 2¹ = 2
0 x 2² = 0
1 x 2³ = 8
1 + 2 + 0 + 8 = 11

Answer:  1011₂ = 11₁₀

Is this look familiar? I learned this during my college but I don’t understand how can we use it. Until…I code.

        static void Main(string[] args)
        {
            Console.WriteLine((7 | 3).ToString());
            Console.WriteLine((7 & 3).ToString());
            Console.Read();
        }

Try to run this code at Visual Studio, and you will have this.

Let’s start the math resolution now.

7 = 111₂ or [2² + 2¹ + 2⁰ = 7] or [4 + 2 + 1 =7]

3 = 11₂ or [2¹ + 2⁰ = 3] or [2 + 1 = 3]

Remembered? logical operator. 1 AND 1 = 1, 1 AND 0 = 0, 1 OR 1 = 1, 1 OR 0 =1…etc.

Let’s start the code now.

Let’s say, we have a survey requirement. See how we can store multiple selection in a field by using bitwise.

public enum Favorites
{
    WCF = 1,
    WPF = 2,
    Web = 4,
    Silverlight = 8,
    None = 0
}

First, we create an Enum class with predefine value for each selection.

    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
        <ContentTemplate>
            <p>
                Please choose your favorite topic[s].
            </p>
            <asp:CheckBox ID="WCF" runat="server" Text="WCF" />
            <br />
            <asp:CheckBox ID="WPF" runat="server" Text="WPF" />
            <br />
            <asp:CheckBox ID="Web" runat="server" Text="Web" />
            <br />
            <asp:CheckBox ID="Silverlight" runat="server" Text="Silverlight" />
            <p>
                <asp:Label ID="Label2" runat="server" Text="Value" AssociatedControlID="DecimalValueText_Get"></asp:Label>
                <asp:TextBox ID="DecimalValueText_Get" runat="server"></asp:TextBox>
                <asp:Button ID="GetValue" runat="server"
                    Text="Get Value" OnClick="GetValue_Click" />
            </p>
            <p>
                <asp:Label ID="Label1" runat="server" Text="Value" AssociatedControlID="DecimalValueText_Set"></asp:Label>
                <asp:TextBox ID="DecimalValueText_Set" runat="server" Text="0"></asp:TextBox>
                <asp:Button ID="SetValue" runat="server"
                    Text="Set Value" OnClick="SetValue_Click" />
            </p>
        </ContentTemplate>
    </asp:UpdatePanel>

        private Int32 Retrieve()
        {
            Int32 result = 0;

            result = WCF.Checked ? (result | Favorites.WCF.GetHashCode()) : result;
            result = WPF.Checked ? (result | Favorites.WPF.GetHashCode()) : result;
            result = Web.Checked ? (result | Favorites.Web.GetHashCode()) : result;
            result = Silverlight.Checked ? (result | Favorites.Silverlight.GetHashCode()) : result;

            return result;
        }

Then, follow by a function to construct a integer value according to the selection.

        private void Display()
        {
            Int32 favorites = int.Parse(DecimalValueText_Set.Text);

            WCF.Checked = ((favorites & Favorites.WCF.GetHashCode()) == Favorites.WCF.GetHashCode());
            WPF.Checked = ((favorites & Favorites.WPF.GetHashCode()) == Favorites.WPF.GetHashCode());
            Web.Checked = ((favorites & Favorites.Web.GetHashCode()) == Favorites.Web.GetHashCode());
            Silverlight.Checked = ((favorites & Favorites.Silverlight.GetHashCode()) == Favorites.Silverlight.GetHashCode());
        }

To make the solution more complete, we create another function to make the selection according to a defined value.

Run the project, now you can select multiple items and click “GetValue” to get the result.

Or, key in a result and let the program to make the selection by click on “SetValue” button.

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