How to select file by using ASP.NET

How to open file dialog in ASP.NET?
We need two controls, one TextBox named txtFile and one Button named btnBrowse.
Add the following code in Page_Load
const string fiName = "fileBrowse";

System.Text.StringBuilder sb = new System.Text.StringBuilder();
sb.Append("<div style='visibility: hidden; width: 0px; height: 0px'>");
sb.Append(string.Format("<input type=file id='{0}' accept='image/gif,image/jpeg'></div>", fiName));
sb.Append("<Script language=JavaScript> function BrowseClick(){");
sb.Append(String.Format("document.forms[0]['{0}'].click();", fiName));
sb.Append(String.Format("document.forms[0]['{0}'].value = document.forms[0]['{1}'].value;", txtFile.ClientID, fiName));
sb.Append("return false;} </Script>");

RegisterClientScriptBlock("scriptKey", sb.ToString());

btnBrowse.Attributes.Add("OnClick", "return BrowseClick();");