ASP.NET Core 中的 DI 异常：无法创建“MyProject.Data.ITableRepositories”类型的实例

Question

我尝试关注 ASP.NET Core 1.1 下的文章 Access Azure Storage in an ASP.NET Core application using Connected Services，以便将我的 Web 应用程序连接到 Azure Tables。

但问题是在 ASP.NET Core 和 Microsoft.WindowsAzure.Storage nuget 下，我无法访问 Syncronous 方法。

我是异步编程的初学者，所以下面的代码可能有点疯狂，但这是我的“异步 Azure 连接器”版本：

// Model
public class Record : TableEntity {
    public Record() { }
    public Record(string id, string name, string partition = "record") {
        this.RowKey = id;
        this.PartitionKey = partition;
        this.Name = name;
    }
    [...]
}    

// Data Interface
public interface ITableRepositories {
    Task<bool> CreateRecordAsync(Record record);
    Task<List<Record>> GetRecordsAsync();
    Task<Record> GetRecordAsync(string key, string partitionKey = "record");
}

// Data Class
public class TableClientOperationsService : ITableRepositories {
    private string connectionString;
    private CloudTable recordTable;

    public TableClientOperationsService() { }
    public TableClientOperationsService(IOptions<AppSecrets> optionsAccessor) {
        connectionString = optionsAccessor.Value.MyProjectTablesConnectionString;
    }

    public CloudTable RecordTable {
        get {
            if (recordTable == null) {
                recordTable = GetTable("Record");
            }
            return recordTable;
        }
    }

    private CloudTable GetTable(string tableName) {
        [.connectionString.]
        table.CreateIfNotExistsAsync().Wait();
        return table;
    }

    public async Task<T> Get<T>(string partitionKey, string rowKey, string tableName) where T : ITableEntity, new()
    {            [...]        }

    public async Task<bool> CreateRecordAsync(Record record) {
        TableOperation insertOperation = TableOperation.Insert(record);
        await this.RecordTable.ExecuteAsync(insertOperation);
        return true;
    }

    public async Task<Record> GetRecordAsync(string key, string partitionKey = "record") {
        const string TableName = "Record";
        Record myRecord = await Get<Record>(partitionKey, key, TableName);
        return myRecord;
    }

    public async Task<List<Record>> GetRecordsAsync() {
        TableQuery<Record> recordsQuery = new TableQuery<Record>().Where(
            TableQuery.GenerateFilterCondition("PartitionKey", QueryComparisons.Equal, "record"));
        EntityResolver<Record> recordResolver = null;
        List<Record> myList = new List<Record>();
        TableQuerySegment<Record> currentSegment = null;
        while (currentSegment == null || currentSegment.ContinuationToken != null) {
            currentSegment = await recordTable.ExecuteQuerySegmentedAsync(
                recordsQuery,
                recordResolver,
                currentSegment != null ? currentSegment.ContinuationToken : null);

            myList.AddRange(currentSegment.Results);
        }
        return myList;
    }
}

// Setup.cs configuration
public void ConfigureServices(IServiceCollection services)
{
    services.AddOptions();
    services.Configure<AppSecrets>(Configuration);

    // association of ITableRepositories with TableClientOperationsService
    services.AddSingleton(typeof(ITableRepositories), typeof(TableClientOperationsService));

    services.AddMvc();        
}


// Usage in the Controller
public class HelloWorldController : Controller {
    public async Task<string> ReadTables1(ITableRepositories repository) {
        StringBuilder response = new StringBuilder();
        response.AppendLine("Here is your Record Table:");
        var items = await repository.GetRecordsAsync();
        foreach (Record item in items) {
            response.AppendLine($"RowKey: {item.RowKey}; Name: {item.Name}");
        }
        return response.ToString();
    }    

但是，当我尝试通过 /HelloWorld/ReadTables1 访问控制器操作时 它给我带来了以下几点：

InvalidOperationException：无法创建“MyProject.Data.ITableRepositories”类型的实例。模型绑定的复杂类型不能是抽象类型或值类型，并且必须具有无参数构造函数。

可能是我在服务中错误地注册了它，因为我的 TableClientOperationsService 类不是抽象的并且具有无参数构造函数？如何解决？

Answer 1

您应该在控制器的构造函数中获取 ITableRepositories 参数，而不是从 DI 获取它的方法。

public class HelloWorldController : Controller
{
    private readonly ITableRepositories _tableRepository;
    public HelloWorldController(ITableRepositories tableRepository)
    {
         _tableRepository = tableRepository;
    }
}