OK , I think you need to retrieve an uploaded image , which is uploaded from your tablet m right ? , then you need to view it into a text area ?
if that is your question , I think you cannot show image into textbox , but you can show it into label.
If you need to know to to upload it into database then retrieve it , please check this link :
and you can retrieve that image into a label by this code base on mentioned link.
If e.Row.RowType = DataControlRowType.DataRow Then
Dim bytes As Byte() = TryCast(TryCast(e.Row.DataItem, DataRowView)("Content"), Byte())
Dim base64String As String = Convert.ToBase64String(bytes, 0, bytes.Length)
Labal1.text = ""
Label code could not be set , please check below link , its an image