How to create a "Many To Many Cascade" Control : The Official Microsoft ASP.NET Forums

// includes...
namespace KHS.Innopas.Web.DynamicData.FieldTemplates
{
    public partial class ForeignKey_EditField : CascadingFieldTemplate
    {
        protected void Page_Init(object sender, EventArgs e)
        {
            // fixed: Assign ListControl information
            ListControl = DropDownList1;


            // add event handler if dependee exists
            if (ParentControl != null)
            {
                // subscribe to event
                ParentControl.SelectionChanged += SelectedIndexChanged;


                // fixed: For performance reasons
                // Make sure, that ParentControl.ListControl has AutoPostBack enabled.
                // Default behaviour for this control was AutoPostBack = True.
                // This caused a full postback for all controls that use this class, even
                // if they don't need to do a postback (because they don't have a parent control).

                if (ParentControl.ListControl != null)
                    ParentControl.ListControl.AutoPostBack = true;
            }
 
        }

}
}

Okay but back to my problem...

This is the new function I've placed in CascadingFieldTemplate.cs

      // advanced populate list control
        protected void PopulateListControl(CheckBoxList listControl, String filterValue)
        {
            //get the parent column
            if (ParentColumn == null)
            {
                // TODO: review this on monday...
                // if no parent column then just call
                // the base to populate the control
                PopulateListControl(listControl);
                // make sure control is enabled
                listControl.Enabled = true;
            }
            else if (String.IsNullOrEmpty(filterValue))
            {
                // if there is a parent column but no filter value
                // then make sure control is empty and disabled
                listControl.Items.Clear();

                if (Mode == DataBoundControlMode.Insert || !Column.IsRequired)
                    listControl.Items.Add(new ListItem("[Not Set]", ""));

                // make sure control is disabled
                listControl.Enabled = false;
            }
            else
            {
                // get the child columns table
                var childTable = ChildrenColumn.ChildTable;

                IList entityList = null;
                ObjectContext objectContext = null;

                if (Mode == DataBoundControlMode.Edit)
                {
                    // Get the real entity from the wrapper
                    object entity = ((ICustomTypeDescriptor)Row).GetPropertyOwner(null);

                    // Get the collection of territories for this employee and make sure it's loaded
                    RelatedEnd entityCollection = (RelatedEnd)Column.EntityTypeProperty.GetValue(entity, null);
                    entityCollection.Load();

                    // Get an IList from it (i.e. the list of territories for the current employee)
                    // REVIEW: we should be using EntityCollection directly, but EF doesn't have a
                    // non generic type for it. They will add this in vnext
                    entityList = ((IListSource)entityCollection).GetList();

                    // Get the current ObjectContext
                    // REVIEW: this is quite a dirty way of doing this. Look for better alternative
                    ObjectQuery objectQuery = (ObjectQuery)entityCollection.GetType().GetMethod(
                        "CreateSourceQuery").Invoke(entityCollection, null);
                    objectContext = objectQuery.Context;
                }
                
                // get query {Table(Details)}
                var query = ChildrenColumn.ChildTable.GetQuery(objectContext);

                // get list of values filtered by the parent's selected entity
                var itemlist = query.GetQueryFilteredByParent(ParentColumn, filterValue).OrderBy(childTable.SortColumn.SortExpression);

                // clear list controls items collection before adding new items
                listControl.Items.Clear();

                // assign all values
                foreach (object row in itemlist)
                {
                    // Create a checkbox for it
                    ListItem listItem = new ListItem(
                        childTable.GetDisplayString(row),
                        childTable.GetPrimaryKeyString(row));

                    if (Mode == DataBoundControlMode.Edit)
                    {
                        // mark assiciated
                        listItem.Selected = entityList.Contains(row);
                    }

                    listControl.Items.Add(listItem);
                }

                // make sure control is enabled
                listControl.Enabled = true;
            }
        }

This function will be called by ManyToMany_Edit.aspx

 using System;
using System.Data;
using System.Data.Objects;
using System.Data.Objects.DataClasses;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Configuration;
using System.Collections;
using System.Collections.Specialized;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Xml.Linq;
using System.Web.DynamicData;

using KHS.Global.Web.DynamicData.CascadeExtensions;

namespace KHS.Innopas.Web.DynamicData.FieldTemplates
{
    public partial class ManyToMany_EditField : CascadingFieldTemplate
    {

        protected void Page_Init(object sender, EventArgs e)
        {
            // add event handler if dependee exists
            if (ParentControl != null)
            {
                // subscribe to event
                ParentControl.SelectionChanged += SelectedIndexChanged;
            }
        }

        public void Page_Load(object sender, EventArgs e) 
        {
            // Register for the DataSource's updating event
            EntityDataSource ds = (EntityDataSource)this.FindDataSourceControl();
    
            // This field template is used both for Editing and Inserting
            ds.Updating += new EventHandler<EntityDataSourceChangingEventArgs>(DataSource_UpdatingOrInserting);
            ds.Inserting += new EventHandler(DataSource_UpdatingOrInserting);

        }

        #region Event
        // consume event
        protected void SelectedIndexChanged(object sender, SelectionChangedEventArgs e)
        {
            PopulateListControl(CheckBoxList1, e.Value);
        }
        #endregion
    
        void DataSource_UpdatingOrInserting(object sender, EntityDataSourceChangingEventArgs e) 
        {
            MetaTable childTable = ChildrenColumn.ChildTable;
    
            // Comments assume employee/territory for illustration, but the code is generic
    
            // Get the collection of territories for this employee
            RelatedEnd entityCollection = (RelatedEnd)Column.EntityTypeProperty.GetValue(e.Entity, null);
    
            // In Edit mode, make sure it's loaded (doesn't make sense in Insert mode)
            if (Mode == DataBoundControlMode.Edit)
                entityCollection.Load();
    
            // Get an IList from it (i.e. the list of territories for the current employee)
            // REVIEW: we should be using EntityCollection directly, but EF doesn't have a
            // non generic type for it. They will add this in vnext
            IList entityList = ((IListSource)entityCollection).GetList();
    
            // Go through all the territories (not just those for this employee)
            foreach (object childEntity in childTable.GetQuery(e.Context))
            {
    
                // Check if the employee currently has this territory
                bool isCurrentlyInList = entityList.Contains(childEntity);
    
                // Find the checkbox for this territory, which gives us the new state
                string pkString = childTable.GetPrimaryKeyString(childEntity);
                ListItem listItem = CheckBoxList1.Items.FindByValue(pkString);
                if (listItem == null)
                    continue;
    
                // If the states differs, make the appropriate add/remove change
                if (listItem.Selected) {
                    if (!isCurrentlyInList)
                        entityList.Add(childEntity);
                }
                else {
                    if (isCurrentlyInList)
                        entityList.Remove(childEntity);
                }
            }
        }
    
        protected void CheckBoxList1_DataBound(object sender, EventArgs e) 
        {
            if (ParentControl != null) 
                PopulateListControl(CheckBoxList1, ParentControl.ListControl.SelectedValue);
            else
                PopulateListControl(CheckBoxList1, "");
        }
    
        public override Control DataControl {
            get {
                return CheckBoxList1;
            }
        }
   }
}

But at the moment I still have a problem with new PopulateListControl function on line 37 after SelectedIndexChanged event was called .

Error says something like "Variable 'Row' can only be used on databound controls" (very bad german/english translation).

Somebody any ideas?

Not today, not tomorrow, but maybe for monday! [:D]

Enjoy your weekend

Loopmaster

Marked as answer by Loopmaster on Jun 23, 2009 06:52 AM

Reply

sjnaughton

All-Star

27330 Points

5459 Posts

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Re: How to create a "Many To Many Cascade" Control

Jun 23, 2009 09:21 AM|LINK

Loopmaster

Error says something like "Variable 'Row' can only be used on databound controls" (very bad german/english translation).

The issue here is you are trying to access Row before the OnDataBound event, because before that is does not contain a valid object. [:D]

See my blog C# Bits | Twitter @sjnaughton
Always seeking an elegant solution.

Reply

Parimal

Member

10 Points

6 Posts

Re: How to create a "Many To Many Cascade" Control

Dec 08, 2009 12:15 AM|LINK

Hi

I am looking for something like that you are doing, Many To Many cascade filter. Is it possible you can share cascade extension so i can implement .

Thanks

How to create a "Many To Many Cascade" Control RSS

10 replies

Loopmaster