try块内赋值，为何不抛出异常就提示使用了未赋值的变量

Question

double Get_Page_Nummber(string tableName)
        {
            //获取搜索结果总共有多少页
            int rows;
            string connectionString = PubConstant.ConnectionString;   //获取连接字符串
            string filter_strsql = Creat_filter_strsql();
            string SQLString = "SELECT count(*) From " + tableName + " " + filter_strsql;
            
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                using (SqlCommand cmd = new SqlCommand(SQLString, connection))
                {
                    try
                    {
                        connection.Open();
                        rows = (int)cmd.ExecuteScalar();
                        
                    }
                    catch (System.Data.SqlClient.SqlException e)
                    //catch
                    {
                        connection.Close();
                        throw e;
                        
                    }
                    return Math.Ceiling(Convert.ToDouble(rows / int.Parse(DropDownList1.SelectedValue)));
                }
            }
            
            //Response.Write(strsql + "        " + roms_number);
            
        }

double Get_Page_Nummber(string tableName)
        {
            //获取搜索结果总共有多少页
            int rows;
            string connectionString = PubConstant.ConnectionString;   //获取连接字符串
            string filter_strsql = Creat_filter_strsql();
            string SQLString = "SELECT count(*) From " + tableName + " " + filter_strsql;
            
            using (SqlConnection connection = new SqlConnection(connectionString))
            {
                using (SqlCommand cmd = new SqlCommand(SQLString, connection))
                {
                    try
                    {
                        connection.Open();
                        rows = (int)cmd.ExecuteScalar();
                        
                    }
                    //catch (System.Data.SqlClient.SqlException e)
                    catch
                    {
                        connection.Close();
                        //throw e;
                        
                    }
                    return Math.Ceiling(Convert.ToDouble(rows / int.Parse(DropDownList1.SelectedValue)));
                }
            }
            
            //Response.Write(strsql + "        " + roms_number);
            
        }

上面的写法是正确的，下面的写法就会提示你使用了未赋值的变量rows。同样是引发异常，一个往外抛出，一个没抛出，从结果来说rows都没被赋值，为啥写法一就是正确的？