我想执行一个选择所有客户的查询,以及每个客户的相应地址。每个客户都可以拥有零个,一个或多个地址。
这是我尝试过的:
sql = "SELECT customers.*, addresses.* FROM customers LEFT JOIN addresses ON addresses.CustomerId = customers.Id ORDER BY customers.Id OFFSET @start ROWS FETCH NEXT @end ROWS ONLY";
List<SqlParameter> parameters = new List<SqlParameter>();
parameters.Add(new SqlParameter("@start", limitStart));
parameters.Add(new SqlParameter("@end", limitEnd));
DataSet set = Db.ExecuteSelectQuery(sql, parameters);
DataTable table = set.Tables["customers"];
Console.WriteLine("Tables count: " + set.Tables.Count); // says there's 1 table.
List<Customer> customers = new List<Customer>();
foreach(DataRow row in table.Rows)
{
Customer cust = new Customer();
cust.Id = row.Field<int>("Id");
cust.ClientNumber = row.Field<string>("clientnumber");
cust.Date = DateTime.Parse(row.Field<string>("date"));
cust.Firstname = row.Field<string>("firstname");
cust.Insertion = row.Field<string>("insertion");
cust.Lastname = row.Field<string>("lastname");
foreach(DataRow addrRow in /* ......?...... */) // Want to loop through addresses of the current customer row.
{
Address address = new Address();
address.Street = addrRow.Field<string>("Street");
address.HouseNumber = addrRow.Field<string>("Number");
address.PostalCode = addrRow.Field<string>("PostalCode");
address.City = addrRow.Field<string>("City");
address.Country = 0;// row.Field<int>("CountryCode");
cust.Addresses.Add(address);
}
customers.Add(cust);
}
return customers;
问题在于我不知道如何使用DataTable
的{{1}}和DataSet
类来处理查询结果。
我在互联网上找不到任何解释您可以访问每个客户所选地址的方式。
有人可以解释一下,或者可能给我看一个代码示例吗?
答案 0 :(得分:0)
您应该过滤属于客户的地址,该客户是循环中的当前客户
您甚至可以使用if
子句将cust.Id
与row.Field<int>("CustomerId")
进行比较
答案 1 :(得分:0)
您可能希望在第二个
中使用linq库 foreach(DataRow addrRow in /* ......?...... */) // Want to loop through addresses of the current customer row.
{
像这样:
foreach(DataRow addrRow in table.Rows.Where(x=>x.Field<int>("Id")==cust.Id)) // Want to loop through addresses of the current customer row.
{
您的代码仍会在客户列表中生成重复的客户条目,因此可能会在第一个foreach循环的顶部添加条件:
foreach(DataRow row in table.Rows)
{
if(customers.Where(x=>x.Id == row.Field<int>("Id").Any())continue;