c#中与vb中CType相同功能的函数，强类型转换

vb: CType(obj,TextBox) CType(Sender,Control)

例如 ： Dim tb1 As TextBox = CType(e.Item.Cells(1).Controls(1), TextBox)

c#: (TextBox)obj

例如 ： TextBox tb = (TextBox) e.Item.Cells[2].Controls[0];

TextBox tb = (TextBox) e.Item.Cells[2].Controls.FindControl("TextBoxID");

Object o;

TextBox tb = (TextBox)o;

TextBox tb2 = o as TextBox;