Dynamic Properties in the PropertyGrid

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Introduction

The article is mainly to explain how to make PropertyGrid show only some properties of a class. One of the big limitations of this control is that it's not possible to hide or show any class properties at runtime.

For example, in an application that I'm developing, I had to show in the PropertyGrid a class that inherits from XMLElement, but I didn't want all the properties of the XMLElement to be shown to the user. One solution was to create a new class that makes access to the main class, but this solution was too less expandable and not useful at runtime. So, I created this control that lets me control the properties shown in the PropertyGrid at runtime too.

Using the code

The class to be shown in the PropertyGrid must inherit from ICustomClass which has only one property, PublicProperties. This is a collection of myPropertys. myProperty implements two properties:

• Name: the name of the property to be shown.
• Category: the name of the category to be shown in the Propertygrid.

interface ICustomClass
{
    PropertyList PublicProperties
    {
        get;
        set;
    }
}

Adding a new property in the Propertygrid is simple:

c.PublicProperties.Add(new myProperty("test3","Category1"));

In this line, we want to show in the PropertyGrid the property "test3" in the category "Category1".

Now, to remove the property from the control:

c.PublicProperties.Remove("test3");

Now, let's check the PropertyGrid. The properties are visualized in the PropertyTab object. So it's necessary to create a new PropertyTab to access the visualized rows. To filter out the properties visualized, I've to override the getProperties method of the PropertyTab class.

This method has an input parameter, the object to be shown in the PropertyGrid. And this object must implement the ICustomClass interface so that I can get the properties I want to display in the PropertyGrid within the GetProperties method.

To get all the properties of the selected object, there's the TypeDescriptor.GetProperties(component). This function returns a PropertyDescriptorCollection filled with all the properties of the class to be shown. But, as I said before, the class to be shown in the PropertyGrid must implement ICustomClass.

So with this row:

//Componet must implement the ICUSTOMCLASS interface.
ICustomClass bclass=(ICustomClass)component;

it's possible to retrieve the list of properties to be shown in the PropertyTab. It's necessary to create a new PropertyDescriptorfor for each new property.

PropertyDescriptor[] propArray = 
        new PropertyDescriptor[bclass.PublicProperties.Count];

Now I've to create the new property that will be shown in the PropertyGrid. So I used TypeDescriptor.CreateProperty from System.ComponentModel.

for (int i=0;i<bclass.PublicProperties.Count;i++)
{
     //Find the list of properties in the array of properties 
     //whose name is in the PubliCProperties
     PropertyDescriptor prop=
             properties.Find(bclass.PublicProperties[i].Name,true);    
     //Build a new properties
     arrProp[i] = TypeDescriptor.CreateProperty(prop.ComponentType, prop, 
            new CategoryAttribute(bclass.PublicProperties[i].Category));
}

At the end of the loop, the arrProp array will be filled up with the new property to be shown in the PropertyTab. Now, since Getproperties has a PropertyDescriptorCollection as return parameter, we can create a new instance of it with:

new PropertyDescriptorCollection(arrProp);

The last step to get everything working, is to override the creation of the PropertyTab of the PropertyGrid.

protected override PropertyTab CreatePropertyTab(Type tabType)

In this function, the base creation of the Propertytab is bypassed, and only the filtered Propertytab is created.

History

• Original article.