How to store combox selected item in variable

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C#

hi I am trying to store value of combo box selected Item in variable.
but it doesn't work properly.

according to my code when I press edit button it fills combo box.

and when index value changes it should show the string which I selected in combobox.

but its shows something like
system.data.datarowview

What I have tried:

private void btnedit_Click(object sender, EventArgs e)
{

cmdpr.Enabled = true;
SqlConnection connection = new SqlConnection(cn);
SqlCommand cmd1 = new SqlCommand("select ProjectName,ProjectID from Project", connection);
SqlDataAdapter da = new SqlDataAdapter(cmd1);
connection.Open();
DataSet ds = new DataSet();
da.Fill(ds, "PN");
cmdpr.DisplayMember = "ProjectName";
cmdpr.ValueMember = "ProjectID";
cmdpr.DataSource = ds.Tables["PN"];
connection.Close();
}

private void cmdpr_SelectedIndexChanged(object sender, EventArgs e)
{
string s = cmdpr.SelectedItem.ToString();
MessageBox.Show(s);

}