Posted By

rengber on 03/27/07

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Last Edited at 03/27/07 08:24pm

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Using a Flag Enumeration with Bitwise Operations

/ Published in: C#

Note the use of the Bitwise Complement Operator ( ~ ) to AND the negative of the bit you want to set.

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[Flags]  
        private enum DeliveryOptions  
        {        
            //Make sure you start with zero and increment by powers of 2.          
            //If you don't assign explicit values VS increments by 1.          
            //Very bad. For example (One | Two = Three)  	
            None = 0,  	//(0000)
            Mail = 1,   	//(0001)
            Email = 2,  	//(0010)
            Fax = 4,  //(0100) 	
        }
        
        private DeliveryOptions deliveryFlags;

private void button2_Click(object sender, EventArgs e)
        {
            //Put some checkboxes on the form.  
            //A [Flag] enum can hold multiple values at once.  
            //Checking or unchecking boxes adds or removes values.  
            MessageBox.Show(deliveryFlags.ToString());
            MessageBox.Show(Convert.ToInt32(deliveryFlags).ToString()); 
        }

private bool CheckFlag(DeliveryOptions targetVal, DeliveryOptions checkVal)
        {
            return ((targetVal & checkVal) == checkVal); 
        }
        private bool HasBeenEmailed(DeliveryOptions targetVal)
        {
            return CheckFlag(targetVal, DeliveryOptions.Email); 
        }

private void btnValueCheck_Click(object sender, EventArgs e)
        {
            bool emailDelivered = HasBeenEmailed(deliveryFlags) ; 
            MessageBox.Show(emailDelivered.ToString()); 
        }

private void chkOne_CheckedChanged(object sender, EventArgs e)
        {
            if (chkMail.Checked)
            {
                deliveryFlags |= DeliveryOptions.Mail; 
            }
            else
            {
                deliveryFlags &= ~DeliveryOptions.Mail; 
            }
        }

private void chkTwo_CheckedChanged(object sender, EventArgs e)
        {
            if (chkEmail.Checked)
            {
                deliveryFlags |= DeliveryOptions.Email;
            }
            else
            {
                deliveryFlags &= ~DeliveryOptions.Email;
            }
        }

private void chkThree_CheckedChanged(object sender, EventArgs e)
        {
            if (chkFax.Checked)
            {
                deliveryFlags |= DeliveryOptions.Fax;
            }
            else
            {
                deliveryFlags &= ~DeliveryOptions.Fax;
            }
        }

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