get values on combobox selection change event in C#.net

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.NET3.5

.NET

private void loadclass()
        {
            string getclass = "select * from class";
            DataTable dt = new DataTable();
            dt = connect.select(getclass);
            comSelClass.DataSource = dt;
            comSelClass.DisplayMember = "class";
            comSelClass.ValueMember = "class_id";
            loadSection();
            loadsubject();
        }
        private void loadSection()
        {
            string getsection = "select section_id, section from section where class_id=" + comSelClass.SelectedValue.ToString();
            DataTable dt = new DataTable();
            dt = connect.select(getsection);
            comSelSection.DataSource = dt;
            comSelSection.DisplayMember = "section";
            comSelSection.ValueMember = "section_id";
        }
private void comSelClass_SelectedIndexChanged(object sender, EventArgs e)
        {
            
        }

what i want is when i change my combobox index i want section related to that class in another combobox. when i have written loadsection() function in comSelClass_SelectedIndexChanged() event i am getting an error : "Unknown column 'System.Data.DataRowView' in 'where clause'"