将属性添加到控件类

Question

I wanna know if it is possible to add attribute to a Control in c#.

I have a method it receive an object in parameter :

    public void CreateTooltip(Object controltoadd = null)
    {
        var myDiv = new HtmlGenericControl("div");
        myDiv.Attributes.Add("width", "100%");

        myDiv.Attributes.Add("onmouseover", "ShowHint('" + this.GetType() + "','test');");
        myDiv.Attributes.Add("onmouseout", "HideHint();");

        if (controltoadd == null)
        {
            List<Control> listcc = new List<Control>();

            for (int i = 0; i < this.Controls.Count; i++)
            {
                Control cc = this.Controls[i];
                string test = cc.GetType().ToString();
                listcc.Add(cc);
            }

            this.Controls.Clear();

            for (int i = 0; i < listcc.Count; i++)
            {
                Control cc = listcc[i];
                myDiv.Controls.Add(cc);
            }
        }
        else
        {
            Control cc = (Control)controltoadd;

            //Don't know what to do here...
        }

        this.Controls.Add(myDiv);
    }

If the object is null, I create a HtmlGenericControl("div") and then I add the Attributes I want. But the problem is when the Object is not null, I convert it to Control , and the property Attributes is not available. I use control because I never know which is the type of the object I received in the parameter.

Answer 1

You need to cast it as a WebControl or a HtmlGenericControl I believe. Control does not contain the property Attributes . You can test what the object you pass is by using is .

if (control is WebControl)
{
    var webControl = (WebControl)control;
}

Or if you prefer to use as :

var webControl = control as WebControl;

if (webcontrol != null)
{
    // code
}

Answer 2

So if it's actually a WebControl (child-class of Control ) then you can cast it to it and use it's Attributes property . Control itself has no property Attributes as you've already noticed:

WebControl wc = controltoadd as WebControl;
if(wc != null)
{
    // wc.Attributes.Add...
}

If it's a HtmlControl cast it to that:

else
{
    HtmlControl hc = controltoadd as HtmlControl;
    if(hc != null)
    {
        // hc.Attributes.Add...
    }
}

Another option would be to make it a generic method that accepts only controls that implement IAttributeAccessor . Both, HtmlControl and WebControl implement that interface to get/set attributes.:

public void CreateTooltip<T>(T controlToAdd)where T: IAttributeAccessor, Control
{
    // ....
    controlToAdd.SetAttribute("width", "100%");
}