Azure Connection String - Object Reference not set to an Instance of an Object

问题

I'm trying to download azure blobs in a Windows Console Application. When I build and debug the application my azure connection string is throwing an exception. This string works fine in my other asp.net app.

The offending line is:

CloudStorageAccount storageAccount = CloudStorageAccount.Parse(ConfigurationManager.ConnectionStrings["DefaultEndpointsProtocol=https;AccountName=xxxxx;AccountKey=xxxxx==;BlobEndpoint=https://xxxxx.blob.core.windows.net/;TableEndpoint=https://xxxxx.table.core.windows.net/;QueueEndpoint=https://xxxxx.queue.core.windows.net/;FileEndpoint=https://xxxxx.file.core.windows.net/"].ConnectionString);

My code is:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Collections;
using Microsoft.WindowsAzure;
using Microsoft.WindowsAzure.Storage;
using Microsoft.WindowsAzure.Storage.Auth;
using Microsoft.WindowsAzure.Storage.Blob;
using System.Configuration;
using System.IO;
using System.Data;
using System.Data.SqlClient;
using System.Threading;

namespace CPGetAdverts
{
    class Program
    {
        static void Main(string[] args)
        {
            // Retrieve storage account from connection string.
            CloudStorageAccount storageAccount = CloudStorageAccount.Parse(ConfigurationManager.ConnectionStrings["DefaultEndpointsProtocol=https;AccountName=xxxxx;AccountKey=xxxxx==;BlobEndpoint=https://xxxxx.blob.core.windows.net/;TableEndpoint=https://xxxxx.table.core.windows.net/;QueueEndpoint=https://xxxxx.queue.core.windows.net/;FileEndpoint=https://xxxxx.file.core.windows.net/"].ConnectionString);
            // Create the blob client.
            CloudBlobClient blobClient = storageAccount.CreateCloudBlobClient();
            // Retrieve a reference to a container.
            var container = blobClient.GetContainerReference("newadverts").ListBlobs();
            // Retrieve filenames from container List
            var urls = new List<string>();
            int fileName = 1;

            foreach (var blob in container)
            {
                using (var fileStream = System.IO.File.OpenWrite(@"\home\pi\Pictures\" + fileName + ".jpg"))
                {
                    var blobReference = blobClient.GetBlobReferenceFromServer(blob.Uri);
                    blobReference.DownloadToStream(fileStream);
                    fileName++;
                }
            }

        }
    }
}

The exception is:

System.NullReferenceException was unhandled HResult=-2147467261
Message=Object reference not set to an instance of an object.
Source=CPGetAdverts StackTrace: at CPGetAdverts.Program.Main(String[] args) in c:\Users\Diarmaid\Documents\Visual Studio 2015\Projects\CPGetAdverts\CPGetAdverts\Program.cs:line 24 at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args) at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart() InnerException:

Does anyone have any ideas please?

回答1:

I would expect ConfigurationManager.ConnectionStrings[""] to reference the name of the connection string, not the connection string itself. The call to retrieve the connection string is unnecessary if are hard-coding it.

See this question for details.

来源：https://stackoverflow.com/questions/35188670/azure-connection-string-object-reference-not-set-to-an-instance-of-an-object