public interface IData
{
    string DataName { get; set; }
}

public class TextBox : System.Windows.Forms.TextBox, IData
{
    public string DataName { get; set; }
}

public static class Ext
{
     public static TResult Find<TResult>(this Control.ControlCollection @this, string filedName)
            where TResult : Control, IData
        {
            TResult result = default(TResult);
            foreach (var control in @this)
            {
                IData iData = control as IData;
                if (null == iData) continue;
                if (iData.FieldName == filedName)
                {
                    result = control as TResult;
                    break;
                }
            }
            return result;
        }
}