Universal control to use in datagrid

Question

4.00/5 (1 vote)

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Hello!

I have the following requirement: I have a list of object instances where each instance has a property of a type I do not know at runtime (e.g. DateTime, string or int). I want to fill a datagrid with that list and for the afore mentioned property, show the appropriate editor when the cell is selected.

I am trying to accomplish this with a custom control like the code shows below:

C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

namespace DataGridExample
{
    public class UniversalControl : ContentControl
    {
        public UniversalControl()
        {
            this.DefaultStyleKey = typeof(UniversalControl);
        }

        public object Value
        {
            get
            {
                return this.GetValue(ValueProperty);
            }
            set
            {
                this.SetValue(ValueProperty, value);
            }
        }

        public static readonly DependencyProperty ValueProperty =
            DependencyProperty.Register(
                "Value",
                typeof(object),
                typeof(UniversalControl),
                new PropertyMetadata(null, ValuePropertyChanged));

        private static void ValuePropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs eventArgs)
        {
            DatePicker picker = new DatePicker();
            if (eventArgs.NewValue != null && eventArgs.NewValue is DateTime)
                picker.SelectedDate = (DateTime)eventArgs.NewValue;

            ((UniversalControl)sender).Content = picker;
            ((UniversalControl)sender).Visibility = Visibility.Visible;
        }

        public override void OnApplyTemplate()
        {
             base.OnApplyTemplate();
        }
    }
}

So, in the valuechanged handler I create the control which goes with the bound value (in this example only the datepicker, but it is about the idea).

Anyway, the result is that I do not see anything happening, while the debugger stops in the handler and I can see the code creating the control being executed.

Anyone has an idea what this could be?

Regards, Perry

Posted 29-Mar-11 10:08am

Perry Bruins

Updated 29-Mar-11 14:17pm

Henry Minute

v2

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Venkatesh Mookkan · Accepted Answer · 2011-03-29T16:12:00

You can accomplish this using CellTemplate (the property name should be similar) for the Column.

Write a DataTemplate with DataTriggers. These DataTrigger would help in showing and hiding the different controls.

Lets go to your problem:
Did you checked whether the ValueChanged handler executes all the times (it should be equal to the number of items in the list)?

Thing I noticed:
Even the data is not DateTime it would show the control. It should be like below

C#

if (eventArgs.NewValue != null && eventArgs.NewValue is DateTime)
{
    picker.SelectedDate = (DateTime)eventArgs.NewValue;
    ((UniversalControl)sender).Content = picker;
    ((UniversalControl)sender).Visibility = Visibility.Visible;
}

The below code might throw runtime error if the eventArgs.NewValue is null. Avoid using && operator while checking for != null

C#

if (eventArgs.NewValue != null &amp;&amp; eventArgs.NewValue is DateTime)

Suggestion:
Instead of casting UniversalControl everytime you can define a variable at the beginning of the method and start using it.

Update:
UniversalControl style doesn't have any ContentPresenter to show the Content you add dynamically from the codebehind.

It should be like below:

XML

<Style TargetType="local:UniversalControl">
        <setter property="Template">
            <setter.value>
                <controltemplate targettype="local:UniversalControl">
                    <border removed="{TemplateBinding Background}">
                            BorderBrush="{TemplateBinding BorderBrush}"
                            BorderThickness="{TemplateBinding BorderThickness}">
                        <contentpresenter />
                    </border>
                </controltemplate>
            </setter.value>
        </setter>
    </Style>

See, I have added a ContentPresenter to show the Content. :)

Mark it as Answer if it is helpful.