asp.net:query with multiple where conditions - mysql

Question

1. I have query.But couldn't add second where condition.Please suggest me the correct semantic .
2. And how can fetch the data from dropdownlist and show it in gridview.
3. How can i fetch value from Tution fee Column of my database when condition satisfies ,and Hostel Fee on fail of condition.??
protected void BindGridview()
{
constr = ConfigurationManager.ConnectionStrings["connstring_DETMIS"].ToString(); // connection string
// String FID = DropDownList1.SelectedItem.Value;
using (var conn = new MySql.Data.MySqlClient.MySqlConnection(constr)) {
conn.Open();
using (var cmd = new MySql.Data.MySqlClient.MySqlCommand("select * from fees_collect_category" + " where F_id =" + DropDownList1.SelectedItem.Value " and C_id=" + DropDownList2.SelectedItem.Value, conn)) {
using (var reader = cmd.ExecuteReader()) {
if (reader.HasRows) {
gvDetails.DataSource = reader;
gvDetails.DataBind();
} else
lblWarning.Text = "There are no records..";
}
}
}
}

Answer 1

Welcome to Stackoverflow. You should first research on the google as why you are not able to add multiple conditions(It's just because of simple syntax mistake).
The exact code of line would be something like this.
using (var cmd = new MySql.Data.MySqlClient.MySqlCommand("select * from fees_collect_category" +
" where F_id = '" + DropDownList1.SelectedItem.Value + "' and C_id=" + DropDownList2.SelectedItem.Value + "'", conn))
NOTE:- As a fellow developer, I won't suggest you to do this by passing values from here as it is dangerous and prone to SQL INJECTION
I would rather tell you to go by using Parameterized queries
Hope that helps and for future go for the Parametrized ones, as it is easy and technically preffered.

Answer 2

protected void BindGridview()
{
String strConnString = ConfigurationManager
.ConnectionStrings["connstring_DETMIS"].ConnectionString;
String strQuery = "select * from student_details " +
"where F_id=#F_Id and C_id=#C_Id";
MySqlConnection con = new MySql.Data.MySqlClient.MySqlConnection(strConnString);
MySqlCommand cmd = new MySql.Data.MySqlClient.MySqlCommand();
cmd.Parameters.AddWithValue("#F_Id",
DropDownList1.SelectedItem.Value);
cmd.Parameters.AddWithValue("#C_Id",
DropDownList2.SelectedItem.Value);
cmd.CommandType = CommandType.Text;
cmd.CommandText = strQuery;
cmd.Connection = con;
try
{
con.Open();
gvDetails.DataSource = cmd.ExecuteReader();
gvDetails.DataBind();
}
catch (Exception ex)
{
throw ex;
}
}