Question

我想在实体框架中从地址表返回4列。但是它在＆＃34; address = addressData.toString（）;＆＃34;说不能隐式地将类型字符串转换为System.Collection.Generic.List

[WebMethod]
    public List<string> getAddressSearchSimple(string addressInput)
    {

        List<string> address = new List<string>();
        try
        {
            using (GISAddressEntities database = new GISAddressEntities())
            {
                var addressData = (from table in database.view_COBADDRESS
                                   where table.ADD_FULL.Contains(addressInput)
                                   select new { table.ADD_FULL, table.POSTALCITY, table.STATE, table.ZIP5});
                address = addressData.ToString();
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }

        return address;
    }

Answer 1

address是一个字符串列表，因此您不能将任何对象设置为ToString（）。

如果addressData应该是一个字符串列表来尝试这个：

var addressData = (from table in database.view_COBADDRESS
               where table.ADD_FULL.Contains(addressInput)
               select new { table.ADD_FULL, table.POSTALCITY, 
               table.STATE, table.ZIP5}).ToList();

Answer 2

从您的问题来看，我认为这可能是您正在寻找的：

address = addressData.ToList().Select(addr => string.Format("{0} {1} {2} {3}", addr.ADD_FULL, addr.POSTALCITY, 
           addr.STATE, addr.ZIP5)).ToList();

Answer 3

您应该调用ToList（）方法而不是ToString（）来创建List。您还应该从查询中选择字符串以获得List<string>。试试这个：

public List<string> getAddressSearchSimple(string addressInput)
{

    List<string> address = new List<string>();
    try
    {
        using (GISAddressEntities database = new GISAddressEntities())
        {
            var addressData = (from table in database.view_COBADDRESS
                               where table.ADD_FULL.Contains(addressInput)
                               select new { table.ADD_FULL, table.POSTALCITY, table.STATE, table.ZIP5 });

            address = addressData.Select(x => string.Format("{0} {1} {2} {3}", x.ADD_FULL, x.POSTALCITY, x.STATE, x.ZIP5))
                .ToList();
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.Message);
    }

    return address;
}

Answer 4

您的问题是addressData不是字符串列表 - 它是包含select中4个字段的临时类的列表。如果您修改select以仅获取一个字段，则会起作用。

但是，正如你所说，你想要这四个字段，我建议你创建一个名为maybe AddressDetails的新类，每个字段都有一个属性。然后你可以简单地写：

AddressDetails data = (from table in database.view_COBADDRESS
                               where table.ADD_FULL.Contains(addressInput)
                               select new { table.ADD_FULL, table.POSTALCITY, table.STATE, table.ZIP5 });
return data;

更改了要匹配的方法的返回类型。

LINQ with EF，无法将字符串转换为List <string>

4 个答案: