Written by: brettright
Thursday, April 01, 2010 1:47 PM 

I have just quickly created a class that links these combo boxes and does all the filtering for you. The class is incredibly simple but I have found it incredibly usefull on my current project.

This class is included with tests in the Habanero.Faces community project which is due to be released next week.

      ///<summary>
    /// This class solves the fairly generic problem of filtering one ComboBox based on the selected item in another combobox.
    /// The problem is when you have two combo boxes that are linked
    ///     i.e. the data from the first combo box filters the data in the second combo box.
    ///      e.g. Select a Country and you get a filtered list of States for that country.
    ///</summary>
    ///<typeparam name="TParentType">The Type of the Parent Business Object(In our example the Country) </typeparam>
    ///<typeparam name="TChildType">The Type of the Child Business Object (in our example the State)</typeparam>
    public class ComboBoxLinker<TParentType, TChildType>
            where TChildType : class, IBusinessObject, new()
            where TParentType: IBusinessObject
    {
        ///<summary>
        /// The Parent Combo Box Selector in our example the Countries.
        ///</summary>
        public IBOComboBoxSelector ParentSelector { get; private set; }
        /// <summary>
        /// The Child Combo Box Selector in our example the States.
        /// </summary>
        public IBOComboBoxSelector ChildSelector { get; private set; }
        /// <summary>
        /// The name of the relationship that is linking these two Business Objects and hence these two ComboBoxes.
        /// in our example the "States" relationship on the Business Object Country.
        /// </summary>
        public string RelationshipName { get; private set; }
        /// <summary>
        /// The Constructor
        /// </summary>
        /// <param name="parentSelector"></param>
        /// <param name="childSelector"></param>
        /// <param name="relationshipName"></param>
        public ComboBoxLinker(IBOComboBoxSelector parentSelector, IBOComboBoxSelector childSelector, string relationshipName)
        {
            if (parentSelector == null) throw new ArgumentNullException("parentSelector");
            if (childSelector == null) throw new ArgumentNullException("childSelector");
            if (string.IsNullOrEmpty(relationshipName)) throw new ArgumentNullException("relationshipName");
            ParentSelector = parentSelector;
            ChildSelector = childSelector;
            RelationshipName = relationshipName;
            parentSelector.SelectedIndexChanged += this.ParentComboBox_SelectedIndexChanged;
        }

        private void ParentComboBox_SelectedIndexChanged(object sender, System.EventArgs e)
        {
            ChildSelector.BusinessObjectCollection = null;

            var selectedItem = ParentSelector.SelectedItem;
            if (selectedItem == null || Convert.ToString(selectedItem) == "") return;
            TParentType location = (TParentType) selectedItem;
            MultipleRelationship<TChildType> relationship =
                location.Relationships[RelationshipName] as MultipleRelationship<TChildType>;
            if (relationship == null) return;
            ChildSelector.BusinessObjectCollection = relationship.BusinessObjectCollection;
        }
    }

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Tags: Habanero.Faces , User Interface ComboBox

Categories: .NET

Location: Blogs Developing in the Domain

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