Change gridview field type

I'm a newbie in vb.net ! my code working to show my database data on GridView it's work fine but I want to change specific value to Image? my code :

Code:

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Dim img_c As String = "my image Url"
    Dim img_x As String
    Dim constr As String = ("my connection string")
    Dim con As New SqlConnection(constr)
    Dim cmd As New SqlCommand()
    cmd.CommandText = "SELECT * FROM Attendance"
    cmd.Connection = con
    Dim sda As New SqlDataAdapter(cmd)
    Dim dt As New DataTable()
    sda.Fill(dt)
    GridView1.DataSource = dt
    GridView1.DataBind()
    Dim ds As New DataSet
    For i As Integer = 1 To GridView1.Rows.Count - 2
        For s As Integer = 3 To GridView1.Columns.Count - 2
            If GridView1.Rows(i).Cells(s).text ="1" Then
                GridView1.ImageField(img_c)

            End If
        Next
    Next

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my source:

Code:

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<asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="False"
      CellPadding="4" DataKeyNames="std_num"
      Height="448px" Width="1352px" BackColor="White" BorderColor="#3366CC"
      BorderStyle="None" BorderWidth="1px" style="margin-right: 12px">
      <Columns>
          <asp:BoundField DataField="Total" HeaderText="totla" SortExpression="Total" >
          <HeaderStyle ForeColor="White" />
          </asp:BoundField>
          <asp:BoundField DataField="4" HeaderText="4" SortExpression="4"  >
              <HeaderStyle ForeColor="White" />
          </asp:BoundField>
          <asp:BoundField DataField="3" HeaderText="3" SortExpression="3"  >
              <HeaderStyle ForeColor="White" />
          </asp:BoundField>
          <asp:BoundField DataField="2" HeaderText="2" SortExpression="2"  >
              <HeaderStyle ForeColor="White" />
          </asp:BoundField>
          <asp:BoundField DataField="1" HeaderText="1" SortExpression="1"  >
              <HeaderStyle ForeColor="White" />
          </asp:BoundField>
          <asp:BoundField DataField="std_name" HeaderText="std_name"
              SortExpression="std_name" >
              <HeaderStyle ForeColor="White" />
          </asp:BoundField>
          <asp:BoundField DataField="std_num" HeaderText="std_num"
              SortExpression="std_num" ReadOnly="True" >
              <HeaderStyle ForeColor="White" />
          </asp:BoundField>
          <asp:BoundField DataField="No" HeaderText="No" SortExpression="No"
              InsertVisible="False" ReadOnly="True" >
          <HeaderStyle ForeColor="White" />
          </asp:BoundField>
      </Columns>
      <FooterStyle BackColor="#99CCCC" ForeColor="#003399" />
      <HeaderStyle BackColor="#003399" Font-Bold="True" ForeColor="#CCCCFF" />
      <PagerStyle BackColor="#99CCCC" ForeColor="#003399" HorizontalAlign="Left" />
      <RowStyle BackColor="White" ForeColor="Black" BorderColor="#333333"
          Font-Bold="True" HorizontalAlign="Center" VerticalAlign="Middle" />
      <SelectedRowStyle BackColor="#009999" Font-Bold="True" ForeColor="#CCFF99" />
      <SortedAscendingCellStyle BackColor="#EDF6F6" />
      <SortedAscendingHeaderStyle BackColor="#0D4AC4" />
      <SortedDescendingCellStyle BackColor="#D6DFDF" />
      <SortedDescendingHeaderStyle BackColor="#002876" />
  </asp:GridView>

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my issue is change field to Image , there is no GridView image properties