Ado.net combobox problem

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I wanna select from first combobox id of a train and in the second combobox give me the wagon that train has (number of a wagon ) I did a database: that first table stored the train id and the second table stored wagon id + id train foreign key i tried this code and its work but when i choose another id it doesn't change the wagon combobox result

What I have tried:

C#

adapter = new SqlDataAdapter("select * from train", cn);
            SqlCommand cmd = new SqlCommand("select * from train", cn);
            cmd.Parameters.Clear();
            adapter.Fill(ds, "train");
            
            comboBox1.DataSource = ds.Tables["train"];
            comboBox1.DisplayMember = "id";
            comboBox1.ValueMember = "id";
           
            
       adapter = new SqlDataAdapter("select  id_w  from wagon  where id='" + comboBox1.SelectedValue + "'", cn);
        
            
                adapter.Fill(ds, "wagon");

        //    adapter1.SelectCommand.Parameters.Clear();
            comboBox2.DataSource = ds.Tables["wagon"];
                comboBox2.DisplayMember = "id_w";
                comboBox2.ValueMember = "id_w";

Posted 25-Feb-18 4:16am

hussainroyal

Updated 25-Feb-18 18:08pm

Maciej Los

v2

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Maciej Los 25-Feb-18 15:04pm

What's your question?

Richard Deeming 26-Feb-18 10:27am

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[^]

adapter = new SqlDataAdapter("select id_w from wagon where id = @id", cn);
adapter.SelectCommand.Parameters.AddWithValue("@id", comboBox1.SelectedValue);

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Animesh Datta · Answer 1 · 2018-02-25T18:08:00

Hello,
ComboBox.SelectedIndexChanged event occurs when the SelectedIndex property has changed.
You have to pass train_id in train_SelectedIndexChanged event.
i.e.,

private void train_SelectedIndexChanged(object sender,System.EventArgs e)
    {
       //Load the wagon_details and populate in combobox.
    }

thanks