xenadmin/XenAdmin/Controls/DataGridViewEnableableComboBoxCell.cs

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using System;
using System.ComponentModel;
using System.Windows.Forms;

namespace XenAdmin.Controls
{
    /// <summary>
    /// Bespoke ComboBoxCell which allows you to provide IEnableableComboBoxItems to it.
    /// If the item is displayed it will be painted grey and will be non-clickable as it 
    /// is a DataGridViewCell hosting a EnableableComboBox
    /// </summary>
    public class DataGridViewEnableableComboBoxCell : DataGridViewComboBoxCell
    {

        public override string ValueMember
        {
            get { return "IEnableableComboBoxItem"; }
        }

        public override string DisplayMember
        {
            get { return "ToStringProperty"; }
        }

        public override void InitializeEditingControl(int rowIndex, object initialFormattedValue, DataGridViewCellStyle dataGridViewCellStyle)
        {
            base.InitializeEditingControl(rowIndex, initialFormattedValue, dataGridViewCellStyle);

            //Transfer cell value to editing control (EnableableComboBox)
            EnableableComboBoxEditingControl ctl = DataGridView.EditingControl as EnableableComboBoxEditingControl;
            if(ctl != null)
            {
                ctl.SelectedItem = Value ?? DefaultNewRowValue;
            }
        }

        /// <summary>
        /// Type of class that proxies the hosted control
        /// </summary>
        public override Type EditType
        {
            get { return typeof(EnableableComboBoxEditingControl); }
        }

        /// <summary>
        /// Type of object stored by the control behind the selection
        /// </summary>
        public override Type ValueType
        {
            get { return typeof(IEnableableComboBoxItem); }
        }

        public override object DefaultNewRowValue
        {
            get { return null; }
        }

        /// <summary>
        /// Type to display on the UI
        /// </summary>
        public override Type FormattedValueType
        {
            get { return typeof(string); }
        }

        /// <summary>
        /// Parse the data being sent back to the cell from the EnableableComboBox to update the cell
        /// </summary>
        /// <param name="formattedValue"></param>
        /// <param name="cellStyle"></param>
        /// <param name="formattedValueTypeConverter"></param>
        /// <param name="valueTypeConverter"></param>
        /// <returns></returns>
        public override object ParseFormattedValue(object formattedValue, DataGridViewCellStyle cellStyle, 
                                                   TypeConverter formattedValueTypeConverter, TypeConverter valueTypeConverter)
        {
            return formattedValue as IEnableableComboBoxItem;
        }
    }

    /// <summary>
    /// A column to host the bespoke DataGridViewEnableableComboBoxCell in the DataGridView
    /// </summary>
    public class EnableableComboBoxColumn : DataGridViewColumn
    {
        public EnableableComboBoxColumn()
            : base(new DataGridViewEnableableComboBoxCell())
        {
        }

        public override DataGridViewCell CellTemplate
        {
            get
            {
                return base.CellTemplate;
            }
            set
            {
                if (value != null &&
                    !value.GetType().IsAssignableFrom(typeof(DataGridViewEnableableComboBoxCell)))
                {
                    throw new InvalidCastException("Must be a DataGridViewEnableableComboBoxCell");
                }
                base.CellTemplate = value;
            }
        }
    }

}