How to convert string to System.web.httpfilecollection

Question

Hello,
How to convert string to system.web.httpfilecollection.
int FileCount = 0;
for (int j = 0; j <= UOriginalFileName.Length - 1; j++)
{
System.Web.HttpFileCollection orifiles1 = (System.Web.HttpFileCollection)UOriginalFileName[j];
string OriginalFilePath = FullFolderPath + "\\" + UOriginalFileName;
OriFiles1[FileCount].SaveAs(OriginalFilePath);
}
UOriginalFileName contains uploaded files.
once run an application getting error as cannot convert string to system.web.httpfilecollection.