How to Bind the DropdownList to another DropdownList

Hi Ranjeet,

I am sure u have done every thing right just you are missing few silly points.
Please follow the steps below i hope that will solve your problem
a) Bind the college dropdown with college fields in database.
ex
dataset retCollegeName = objDAL.FillCmbCollegeName(objDataset);
cmbCollegeNAme.DataSource = retCollegeName.Tables["CollegeName"];
cmbCollegeNAme.DataTextField = "Name";
cmbCollegeNAme.DataValueField = "OrderSeq";
cmbCollegeNAme.DataBind();
b) go to property of cmbCollegeNAme and set auto postback = true;
c) call a query to fetch department as same defined above from cmbCollegeNAme.SelectedIndexChanged and populate the Department dropdown in the same way as above.

Hope this will solve your problem
Thanks
Amit Dutta

Try This :
make auto postback true Property for College Dropdown.

       if (!IsPostBack)
       {
          FillDropDownList();

        }

 private void FillDropDownList()
    {
        DataSet ds = new DataSet();
        SqlDataAdapter myda = new SqlDataAdapter("Select college  FROM tablename",connection object);
        myda.Fill(ds);
        drop_college.DataSource = ds;
        drop_college.DataValueField = "college";
        drop_college.DataBind();
        drop_college.Items.Insert(0, new ListItem("Select", "0"));
    }


then after double click on college Dropdown.

 protected void drop_college_SelectedIndexChanged(object sender, EventArgs e)
    {
       
        DataSet ds = new DataSet();
        SqlDataAdapter myda = new SqlDataAdapter("Select department FROM tablename where college='"+drop_college.SelectedItem.Value+"'", connection object);
        myda.Fill(ds);
        drop_department.DataSource = ds;
        drop_department.DataValueField = "department";
        drop_department.DataBind();
        drop_department.Items.Insert(0, new ListItem("Select", "0"));
       
    }

Hope this will help You.

where u got stuct. bind the second dropdownlist on first dropdownlist SelectedIndexChanged event. as described in solution 3.

Make sure the auto postback property be set true. This is used to trigger the SelectedIndexChanged event of the dropdownlist

Fill the data for your first dropdown and when the event invoked the code must be like this,

protected void drop_college_SelectedIndexChanged(object sender, EventArgs e)
    {
       
        DataSet ds = new DataSet();
        SqlDataAdapter dataAdapter = new SqlDataAdapter("Select DepartmentName,DepartmentID FROM DepartmentTable where CollegeName='"+ddlCollegecollege.SelectedItem.Value+"'", connection object);
        dataAdapter.Fill(ds);
        ddlepartment.DataSource = ds;
        ddlDepartment.TextValueField = "DepartmentName";
        ddlDepartment.DataValueField = "DepartmentID"
        ddlDepartment.DataBind();
        ddlDepartment.Items.Insert(0, new ListItem("-- Select Department --", "0"));
       
    }

Hope it helps, Happy coding