在 C# 中更新 SQLite 数据库

Question

在我的 Xamarin 应用程序中，有一个 Picker 从数据库中获取银行列表，该数据库通过 API 获取银行详细信息。

一切正常，但是现在，我想更新数据库，如果在 API 中添加了新的银行，我想将它们添加到现有数据库中。

我写了这个小代码，但问题是，它首先从数据库中输出所有现有记录，然后打印新记录，是记录总数的很多倍，例如（如果有十条记录，则每条记录打印十次）。

ViewModel.cs

// Load all Banks into a List
var getBanks = await App.Database.GetBankAsync();

// Update the Bank Details where new Banks doesn't exist in the Database
List<Bank> updateBanks = new List<Bank>();

foreach (Banks i in obj.banks)
{
    foreach (var record in getBanks.Where(c => c.Name != i.alias.name))
    {
        updateBanks.Add(new Bank { Name = i.alias.name, Status = "Not Registered" });
    }
}

foreach (var bank in updateBanks)
{
    await App.Database.SaveBankAsync(bank);
}

// Load all Banks into a List
var getBanksUpdated = await App.Database.GetBankAsync();

// Load the Banks whose Status is "Not Registered"
foreach (var record in getBanks.Where(c => c.Status == "Not Registered")
{
    _bankList.Add(record);
}

public class Alias
{
public string name { get; set; }
}

public class Banks
{
public Alias alias { get; set; }
public string id { get; set; }
}

public class RootObject
{
public List<Banks> banks { get; set; }
}

通过 API 获取的数据

{
    success: true,
    banks: [
        {
        alias: {
        name: "Bank 1",
        Address: "Earth"
        },
        endpoint: {
        uri: "http://127.0.0.1:0000"
        },
        state: "Registered",
        createdAtUtc: "2021-01-19T13:55:12.2318662",
        updatedAtUtc: "2021-01-19T13:55:14.9944042"
        },
    ]
}

从 API 获取数据的代码

HttpClient httpClient = new HttpClient(new NativeMessageHandler());
Uri getDataBanks = new Uri(string.Format("http://127.0.0.1:0000/Banks"));

HttpResponseMessage restponseBanks = await httpClient.GetAsync(getDataBanks);
string contentBanks = await restponseBanks.Content.ReadAsStringAsync();
RootObject obj = JsonConvert.DeserializeObject<RootObject>(contentBanks);

Answer 1

// get the names of all existing banks
List<string> names= obj.banks.Select(u => u.Name).ToList();

// get the names of all banks taken from the API
List<string> names_new= getBanks.Select(u => u.Name).ToList();

foreach (var record in names_new)
{
//check if the bank is exists or not
     if(! names.contains(record)
     {
        updateBanks.Add(new Bank { Name = record.alias.name, Status = "Not Registered" });
     }
}

Answer 2

我不知道你的数据，但你有太多的 foreach 循环，你正在检查每个循环中的整个集合。因此，您的条件可能会在每个循环中捕获每个帐户。