Combox selected value is showing system.Data row cannot convert error

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C#

WinForms

combobox

I fetched all the username in Combobox1 displaymember as username and Id as value member.

Now I enabled a groupbox having a textbox,3 combobox and update button when i select an item in Combobox1.considering the valuemember of combobox1 fetching particular user and trying to display those details in groupbox(textbox contains the username,3 combo boxes having department designation role details) .My Database table having foreign keys(deparment,designation and role).It returns only 3 combobox value members not the display memeber(Text).How can i link these tow so that upon selecteing username in Combobox1 the corresponding values should appear in textbox as well as 3 comboboxes.

here is my code:

private void cmbBoxUpdateEmployee_SelectedIndexChanged_1(object sender, EventArgs e)
    {
          changecmbBoxValue();

    }     panelupdateEmployee.Visible = true;


    public void changecmbBoxValue()
    {

        try
        {
            textBoxUpdateEmployee.Enabled = true;
            cmbBoxUpdateEmpRoleID.Enabled = true;
            cmbBoxUpdateEmpDepartment.Enabled = true;
            cmbBoxUpdateEmpDesignation.Enabled = true;
            dbobj.Open();
            DataSet ds = new DataSet();
            if (!string.IsNullOrEmpty(cmbBoxUpdateEmployee.SelectedValue.ToString()))
            {
                string cmd = "select Name,RoleId,DepartmentId,DesignationId from tblEmployee where Name='" + cmbBoxUpdateEmployee.SelectedValue+ "'";

      //I get system.Datarow conversion not done error.
                ds = dbobj.ExecuteDataset(cmd);
                if ((ds.Tables[0].Rows.Count) > 0)
                {
                textBoxUpdateEmployee.Text = Convert.ToString(ds.Tables[0].Rows[0]          [0].ToString());
              cmbBoxUpdateEmpRoleID.SelectedIndex = Convert.ToInt32(ds.Tables[0].Rows[0][1].ToString());
                    cmbBoxUpdateEmpDepartment.SelectedIndex = Convert.ToInt32(ds.Tables[0].Rows[0][2].ToString());
                    cmbBoxUpdateEmpDesignation.SelectedIndex = Convert.ToInt32(ds.Tables[0].Rows[0][3].ToString());
                    lblupdatedelete.Text = " Update Successfully";
                    EmployeeUpdateInfo();
                    textBoxUpdateEmployee.Clear();
                }
            }              

        }
        catch (Exception ex)
        {
            MessageBox.Show("Error!!" + ex.Message);
        }
        finally
        {
            dbobj.Close();
        }


    }

How can i achieve this? any idea.