ConnectionString 属性尚未初始化。

protected void Button1_Click1(object sender, EventArgs e)
    {
      
        string str = "insert into zxly (name,comname,phone,email,add,title,content) values ('" + name.Text + "','" + comname.Text + "','" + phone.Text + "','" + email.Text + "','" + add.Text + "','" + title.Text + "','" + content.Text + "')";
        OleDbConnection cn = new OleDbConnection(System.Configuration.ConfigurationManager.AppSettings["SQLConnString"].ToString());
        cn.ConnectionString=System.Configuration.ConfigurationManager.AppSettings["SQLConnString"].ToString();
        cn.Open();
        OleDbCommand com = new OleDbCommand(str, cn);
        cn.Close();
      
    }