Исправлено, но все также...

Dim strFilePath As String = Server.MapPath(dsDocData.Tables("NewDocs").Rows(0).Item("Content"))
Dim htmlFile As FileInfo = New FileInfo(strFilePath)
Dim encoding As System.Text.Encoding = System.Text.Encoding.GetEncoding("windows-1251")
Dim objStream As StreamReader = New StreamReader(strFilePath, encoding)
objStream = htmlFile.OpenText
Dim strContents As String = objStream.ReadToEnd

Dim NewControl As New HtmlGenericControl("div")

NewControl.ID = "NewControl"
NewControl.InnerHtml = strContents

ControlContainer.Controls.Add(NewControl)