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Reputation: 13

How can I display data in data grid view

I have a combo box where I show all the names of my tables inside my database. Now I can't find a way where I can display all the content of my table in data grid view by selecting a table name in my combo box. Currently I have 2 tables where I can choose by selecting it in combo box and display its values in data grid view.

What I'am trying to achieve is, by selecting the table names in combo box my data grid view will display the values of the table depending on what table name is selected in my combo box

here is my code:

private void samples_Load(object sender, EventArgs e)
{
    MySqlConnection con = new MySqlConnection(conn);
    try
    {
        con.Open();
        MySqlCommand sqlCmd = new MySqlCommand();

        sqlCmd.Connection = con;
        sqlCmd.CommandType = CommandType.Text;

        sqlCmd.CommandText = "select table_name from information_schema.tables where table_schema = 'attenddb'";

        MySqlDataAdapter sqlDataAdap = new MySqlDataAdapter(sqlCmd);

        DataTable dtRecord = new DataTable();
        sqlDataAdap.Fill(dtRecord);
        comboBox1.DataSource = dtRecord;
        comboBox1.DisplayMember = "TABLE_NAME";
        con.Close();
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
}

private void button1_Click(object sender, EventArgs e)
{
    try
    {
        string query2 = "select table_name from ['"+ comboBox1.Text + "']";
        MySqlConnection con2 = new MySqlConnection(conn);
        MySqlCommand com2 = new MySqlCommand(query2, con2);
        MySqlDataAdapter myadapt = new MySqlDataAdapter();
        myadapt.SelectCommand = com2;
        DataTable dtable = new DataTable();
        myadapt.Fill(dtable);
        dataGridView1.DataSource = dtable;
    }
    catch
    {
        MessageBox.Show("Error Loading data");
    }
}

Upvotes: 0

Views: 2644

Answers (3)

Jingmiao Xu-MSFT
Jingmiao Xu-MSFT

Reputation: 2297

Here are some problems with your code:

  1. We could use "select * from " + comboBox1.Text; to get the data from the database.
  2. It is necessary for us to open the connection before we want to access the database.

If you want to display data in data grid view, you can refer to the following code:

private void Form1_Load(object sender, EventArgs e)
    {
        comboBox1.Items.Add("table_name1");
        comboBox1.Items.Add("table_name2");
    }

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
    {
        string query2 = "select * from " + comboBox1.Text;
        MySqlConnection con2 = new MySqlConnection(conn);
        con2.Open();
        try
        {
            MySqlCommand com2 = new MySqlCommand(query2, con2);
            MySqlDataAdapter myadapt = new MySqlDataAdapter();
            myadapt.SelectCommand = com2;
            DataTable dtable = new DataTable();
            myadapt.Fill(dtable);
            dataGridView1.DataSource = dtable;
        }
        catch
        {
            MessageBox.Show("Error Loading data");
        }
        finally

        {
            if (con2.State == ConnectionState.Open)

            {
                con2.Close();
            }
        }
    }

Upvotes: 0

Olivier Jacot-Descombes
Olivier Jacot-Descombes

Reputation: 112324

You must select all the columns with * from the selected table.

string query2 = "select * from ["+ comboBox1.Text + "]";

or with string interpolation:

string query2 = $"select * from [{comboBox1.Text}]";

And also, do not use single quotes around the table name (you already have the square brackets), since you want the name directly and not as string literal.

Upvotes: 0

Bastin Francis
Bastin Francis

Reputation: 1

Don't use Bracket [] and single quotes.

string query2 = "select columnname from " + comboBox1.Text+ "";

Upvotes: 0

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