Read text file from Assets

dear team.

when i try to read and write a text file which is located in Assets folder . result shows file not found exception. following is my code.

Dim list1 As List
Dim st As InputDialog
Dim str As String
st.Show("Enter Phone no","TEST","OK","CANCEL","",Null)
str=st.Input
Msgbox(str,"")
File.OpenInput(File.DirAssets,"phoneno.txt")
list1=File.ReadList(File.DirAssets,"phoneno.txt")
For i=0 To list1.Size-1
Log(list1.Get(i))
Next
File.WriteString(File.DirAssets,"phoneno.txt",str)