How to search using gridview

Public Partial Class WebForm3
    Inherits System.Web.UI.Page
    Public oCn As New System.Data.SqlClient.SqlConnection("Data Source=(local);Initial Catalog=MyDatabase;Uid=sa")

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        If Me.IsPostBack = False Then
            fill_ddl()
        End If
    End Sub

    Protected Sub DropDownList1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles DropDownList1.SelectedIndexChanged
        fill_data()
    End Sub

    Sub fill_data()
        If oCn.State = ConnectionState.Closed Then
            oCn.Open()
        End If

        Dim cmd As New SqlClient.SqlCommand("select * from mst_employees where name='" & Me.DropDownList1.SelectedItem.Text & "'", oCn)
        Dim da As New SqlClient.SqlDataAdapter(cmd)
        Dim ds As New DataSet("bpl")
        Dim i As Integer = 0

        da.Fill(ds, "bpl")
        Me.GridView1.DataSource = ds.Tables(0)
        Me.GridView1.DataBind()
        oCn.Close()
    End Sub

    Sub fill_ddl()
        If oCn.State = ConnectionState.Closed Then
            oCn.Open()
        End If

        Dim cmd As New SqlClient.SqlCommand("select name from mst_employees", oCn)
        Dim da As New SqlClient.SqlDataAdapter(cmd)
        Dim ds As New DataSet("bpl")
        Dim i As Integer = 0

        da.Fill(ds, "bpl")
        If ds.Tables(0).Rows.Count > 0 Then
            Me.DropDownList1.Items.Add("Select an Item")
            While (i <> ds.Tables(0).Rows.Count)
                Me.DropDownList1.Items.Add(ds.Tables(0).Rows(i).Item("Name").ToString)
                i = i + 1
            End While
        End If
        Me.DropDownList1.DataBind()
        oCn.Close()
    End Sub
End Class