Some of My Favorite Extension Methods

There has been some discussion about extension methods and how they should be used and when. Personally, I try to use them when it will increase the readability of my code. A common candidate for extension methods is the static helper method. These mostly take the form of something like:

public static class StringHelper
{
     public static string Truncate(string s, int maxLength);
}

And is usually consumed with something like:

string newString = StringHelper.Truncate(myString, 10);

Now, this isn't too bad, but with extension methods, the signature for this method now looks like:

public static string Truncate(this string s, int maxLength)

and is used with syntax like the following:

string newString = myString.Truncate(10);

So I hope you agree that this improves readability and understanding. And it also prevents you from sprinkling "MyHelperClass.MyMethod" calls everywhere.

I thought I would share some of the extension methods that I am finding invaluable.

RenderControl

This method allows you to take and WebControl and render it as a string. This is very useful for html code generation. The method signature for the helper method is:

public static string RenderControl(WebControl control);

Since the syntax to use extension methods is slightly different than static methods, I decided to rename this method to RenderAsString:

publicstatic string RenderAsString(this WebControl control)
{
    StringBuilder sb = new StringBuilder();
    using (StringWriter sw = new StringWriter(sb))
    {
        using (HtmlTextWriter tw = new HtmlTextWriter(sw))
        {
            control.RenderControl(tw);
            return sb.ToString();
        }
    }
}

GetTableCell

This method has many overloads so you can get all of them in the attached download. I will just show one here:

public static void Add(this TableCellCollection cells,
                       string text, string cssClass, int? columnSpan)
{
    TableCell cell = new TableCell();
    cell.Text = text;
    if (!String.IsNullOrEmpty(cssClass))
        cell.CssClass = cssClass;
    if (columnSpan.HasValue)
        cell.ColumnSpan = columnSpan.Value;
    cells.Add(cell);
}

The Syntax for using this is something like:

Table table = new Table();
TableRow tr = new TableRow();
tr.Cells.Add("My Cell", "MyCssClass", 2);

Which is much better than:

tr.Cells.Add(HtmlHelper.GetTableCell("My Cell", "MyCssClass", 2));

These are just a couple of small examples of how I am finding Extension methods a great tool for making code more readable and concise. You can download the source code for both of these methods here:

HtmlHelper.cs