Insert Update Save Delete Using textbox in vb.net-1

Imports System.Data.SqlClient

Module Module1
Public con As New SqlConnection("workstation id=""HOME-6TIW5FOKEY"";packet size=4096;user id=sa;initial catalog=pint" & _
    "u;persist security info=False")
    Public com As SqlCommand
    Public sqlda As SqlDataAdapter
    Public ds As DataSet
    Public str As String
    Public dt As DataTable
    Public dr As DataRow
    Public dc As DataColumn
    Public bm As BindingManagerBase
    Public flag As Byte
    Public objcom As SqlCommandBuilder

End Module

Imports System.Data.SqlClient

Public Class Form1
    Inherits System.Windows.Forms.Form

    Dim bm As BindingManagerBase

Private Sub btnload1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnload1.Click

        str = "select * from student"
        com = New SqlCommand(str, con)
        sqlda = New SqlDataAdapter(com)
        ds = New DataSet
        sqlda.Fill(ds, "student")
        'dt = ds.Tables("student")
        txtid.DataBindings.Add("Text", ds, "student.sid")
        txtname.DataBindings.Add("Text", ds, "student.sname")
        txtmarks.DataBindings.Add("Text", ds, "student.smarks")
        txtaddress.DataBindings.Add("Text", ds, "student.saddress")
        txtyear.DataBindings.Add("Text", ds, "student.year")
        bm = Me.BindingContext(ds, "student")
        bm.Position = 0
  Label6.Text = ((Me.BindingContext(ds, "student").Position + 1).ToString + " of ") & Me.BindingContext(ds,  "student").Count.ToString

    End Sub


Private Sub btnfirst_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnfirst.Click

        bm.Position = 0
Label6.Text = ((Me.BindingContext(ds, "student").Position + 1).ToString + " of ") & Me.BindingContext(ds, "student").Count.ToString

    End Sub

    Private Sub btnnext_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnnext.Click

        bm.Position += 1
  Label6.Text = ((Me.BindingContext(ds, "student").Position + 1).ToString + " of ") & Me.BindingContext(ds, "student").Count.ToString

    End Sub

    Private Sub btnprevious_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnprevious.Click

        bm.Position -= 1
  Label6.Text = ((Me.BindingContext(ds, "student").Position + 1).ToString + " of ") & Me.BindingContext(ds, "student").Count.ToString

    End Sub

    Private Sub btnlast_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnlast.Click

        bm.Position = bm.Count - 1
  Label6.Text = ((Me.BindingContext(ds, "student").Position + 1).ToString + " of ") & Me.BindingContext(ds, "student").Count.ToString

    End Sub

    Private Sub btnadd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnadd.Click

        txtid.Text = ""
        txtname.Text = ""
        txtaddress.Text = ""
        txtmarks.Text = ""
        txtyear.Text = ""
        flag = 1
        txtid.Focus()

    End Sub

    Private Sub btnmodify_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnmodify.Click

        flag = 2

    End Sub

    Private Sub btnsave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnsave.Click

        Try
            If flag = 1 Then

                con.Open()
str = "insert into student values('" & txtid.Text.Trim & "','" & txtname.Text.Trim & "'," & txtmarks.Text.Trim & ",'" & txtaddress.Text.Trim & "','" & txtyear.Text.Trim & "')"
                com = New SqlCommand(str, con)
                com.ExecuteNonQuery()
                con.Close()
                MsgBox("Records Successfuly Inserted")
                txtid.Clear()
                txtname.Clear()
                txtmarks.Clear()
                txtaddress.Clear()
                txtyear.Clear()

            ElseIf flag = 2 Then

                con.Open()
str = "update student set sname='" & txtname.Text.Trim & "',smarks=" & txtmarks.Text.Trim & ",saddress='" & txtaddress.Text.Trim & "',year='" & txtyear.Text.Trim & "' where sid='" & txtid.Text.Trim & "'"
                com = New SqlCommand(str, con)
                com.ExecuteNonQuery()
                con.Close()
                MsgBox("Records Successfuly Updated")
            End If

        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

    End Sub

    Private Sub btndelete_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btndelete.Click

        Try
str = "delete from student where sid='" & txtid.Text.Trim & "'"
            com = New SqlCommand(str, con)
            con.Open()
            com.ExecuteNonQuery()
            MsgBox("Records Successfuly Deleted")
            con.Close()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

    End Sub




    Private Sub btnload_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnload.Click

        Try
            con.Open()
            str = "select * from student"
            com = New SqlCommand(str, con)
            sqlda = New SqlDataAdapter(com)
            ds = New DataSet
            sqlda.Fill(ds, "student")
            DataGrid1.DataSource = ds
            DataGrid1.DataMember = "student"
            con.Close()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
    End Sub

    Private Sub btnclose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnclose.Click

         Application.Exit()

    End Sub

    Private Sub btnmaxmarks_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnmaxmarks.Click

        Try
            con.Open()
            str = "select max(smarks)from student"
            com = New SqlCommand(str, con)
            txtmaxmarks.Text = com.ExecuteScalar
            con.Close()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
     End Sub

    Private Sub btnminmarks_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnminmarks.Click

        Try
            con.Open()
            str = "select min(smarks)from student"
            com = New SqlCommand(str, con)
            txtminmarks.Text = com.ExecuteScalar
            con.Close()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
    End Sub
End Class