Can't get the grid view data and store it to database

Question

1.00/5 (1 vote)

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<pre><div class="container">
    <asp:GridView ID="GridView1" runat="server"  AutoGenerateColumns="False" Font-Size="Medium">

<asp:TemplateField HeaderText="Student ID">
  <ItemTemplate>
     <asp:Label ID="lblID" runat="server"   Width="80px"  Text='<%#Eval("studentID") %>'/>
 </ItemTemplate>


  <asp:TemplateField HeaderText="">
        <ItemTemplate>                                     
                  <asp:LinkButton runat="server"  OnCommand="LinkButton_Click" Text=" VoteCandidate"> </asp:LinkButton>     
         </ItemTemplate>



 </asp:GridView>

    <div>
        <asp:Label ID="Label1" runat="server" ></asp:Label>
    </div>
</div>

Here is my form to show the gridview.

What I have tried:

C#

protected void loadCandidate()
    {
        con.Open();
        MySqlCommand cmd = new MySqlCommand("select studentID from candidate where faculty='FOCS'", con);
        MySqlDataReader dr = cmd.ExecuteReader();
        if (dr.HasRows == true)
        {
            GridView1.DataSource = dr;
            GridView1.DataBind();
        }
    }


    protected void LinkButton_Click(Object sender, EventArgs e)
    {
        String MyConnection2 = "Server=localhost;database=ovs;Uid=root;password=; Convert Zero Datetime=True";
        foreach (GridViewRow g1 in GridView1.Rows)
        {
            MySqlConnection MyConn2 = new MySqlConnection(MyConnection2);
            
            String query = "insert into voting (studentID)values ('" + g1.Cells[0].Text + "')" ;
            MySqlCommand MyCommand2 = new MySqlCommand(query, MyConn2);
         
          MySqlDataReader MyReader2;
          MyConn2.Open();
          MyReader2 = MyCommand2.ExecuteReader();
          MyConn2.Close();
        }

    }

When I execute the sql insert command, no error occur, but I expect the studentID that displayed in the gridview being stored in the voting table, but the studentID on the voting table are empty

Posted 4-Aug-20 19:22pm

ycwong99

Updated 4-Aug-20 20:15pm

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Comments

Richard Deeming 5-Aug-20 7:55am

Your code is vulnerable to SQL Injection[^]. NEVER use string concatenation to build a SQL query. ALWAYS use a parameterized query.

Everything you wanted to know about SQL injection (but were afraid to ask) | Troy Hunt[^]
How can I explain SQL injection without technical jargon? | Information Security Stack Exchange[^]
Query Parameterization Cheat Sheet | OWASP[^]

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Sandeep Mewara · Answer 1 · 2020-08-04T20:15:00

For Insert, you need to try with ExecuteNonQuery on command and not ExecuteReader. ExecuteReader would not edit/update data in database.

Please read here about ADO.NET and try: Accessing data with ADO.NET[^]

Example:

C#

private void button1_Click(object sender, EventArgs e)
        {
            string connetionString = null;
            SqlConnection cnn ;
            SqlCommand cmd ;
            string sql = null;

            connetionString = "Data Source=ServerName;Initial Catalog=DatabaseName;User ID=UserName;Password=Password";
            sql = "<Your INSERT SQL Statemnt Here>";

            cnn = new SqlConnection(connetionString);
            try
            {
                cnn.Open();
                cmd = new SqlCommand(sql, cnn);
                cmd.ExecuteNonQuery();
                cmd.Dispose();
                cnn.Close();
                MessageBox.Show (" ExecuteNonQuery in SqlCommand executed !!");
            }
            catch (Exception ex)
            {
                MessageBox.Show("Can not open connection ! ");
            }
        }