conversion failed when converting the varchar value to data type int when using executenonquery()

I am trying to read a single value  from the database into a string using the executenonquery() Method and an stored proc but get the error conversion failed when converting the varchar value to data type int

any ideas ?
below is the code
protected void Button2_Click(object sender, EventArgs e)
{
string CStr = ConfigurationManager.ConnectionStrings["app"].ConnectionString.ToString();
SqlCon ...