Select next item from combo box if the selected item exists in SQL server database

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C#

SQL

Visual-Studio

combobox

On my Windows form, there are two comboboxes showing name of specific courses and number of sections respectively. But, I want to write some codes for my combobox (number of sections) that makes it enable to choose the correct section number automatically. For example, for course C#, if section one is inserted into SQL Server, the combobox for section number should select section two for that course.

SqlConnection objConnection = new SqlConnection(@"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename=C:\UniversityDataBase.mdf;Integrated Security=True");

private void CourseName_Click(object sender, EventArgs e)
{
    string query = "SELECT *FROM CourseTable";

    SqlDataAdapter SDA = new SqlDataAdapter(query, objConnection);
    DataTable dt = new DataTable();
    SDA.Fill(dt);

    comboBox1.DataSource = dt;
    comboBox1.DisplayMember = "Coursename";
    objConnection.Close();
}

private void SectionNo_Click(object sender, EventArgs e)
{
    string query = "SELECT * FROM SecNo";

    SqlDataAdapter SDA = new SqlDataAdapter(query, objConnection);
    DataTable dt = new DataTable();
    SDA.Fill(dt);

    comboBox2.DataSource = dt;
    comboBox2.DisplayMember = "SectoinNumber";

    objConnection.Close();
}

What I have tried:

c# - Select Next Item from Combo Box if the item exists in SQL Server database - Stack Overflow[^]