AWS Lambda access local resource or storage C#

Question

How can I store and access a file in Lambda using C# I used the tmp folder that is available for the lambda but I get an error of could not load file or assembly. How can I solve the error? I used the ADP nuget.

        using (WebClient webClient = new WebClient())
        {
            webClient.DownloadFile(reportLine, Path.GetTempPath() + 
            "sample_auth.key");
        }

I used this to download the file into the tmp folder of the lambda. I did not include the other config in the string confidential but you can check the github below for the exact same sample.

    string config = @"{
           ""sslCertPath"": ""/tmp/sample.pfx"",
           ""sslKeyPath"": ""/tmp/sample_auth.key"",
           }";

        ADPAccessToken token = null;

        if (String.IsNullOrEmpty(clientconfig))
        {
            Console.WriteLine("Settings file or default options not available.");
        }
        else
        {
              ClientCredentialConfiguration connectionCfg = JSONUtil.Deserialize<ClientCredentialConfiguration>(clientconfig);
              ClientCredentialConnection connection = (ClientCredentialConnection)ADPApiConnectionFactory.createConnection(connectionCfg);

            //context.Logger.Log(ADPApiConnection.certificatepath);
            //context.Logger.Log(clientconfig);
            try
            {
                connection.connect();
                if (connection.isConnectedIndicator())
                {
                token = connection.accessToken;

                    //    context.Logger.Log("Connected to API end point");
                    //    //Console.WriteLine("Token:  ");
                    //    //Console.WriteLine("         AccessToken: {0} ", token.AccessToken);
                    //    //Console.WriteLine("         TokenType: {0} ", token.TokenType);
                    //    //Console.WriteLine("         ExpiresIn: {0} ", token.ExpiresIn);
                    //    //Console.WriteLine("         Scope: {0} ", token.Scope);
                    //    //Console.WriteLine("         ExpiresOn: {0} ", token.ExpiresOn);
                    //    //Console.ReadLine();
                }
            }
            catch (ADPConnectionException e)
            {
                context.Logger.Log(e.Message);
            }
            //catch (Exception e)
            //{
            //    context.Logger.Log(e.Message);
            //}
            //Console.Read();
        }

        return "Ok";
    }

I get an error of I think lambda check the /var/task folder

errorMessage": "One or more errors occurred. (Could not load file or 
assembly 'System.Net.Http.WebRequest, Version=4.0.0.0, Culture=neutral, 
PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file 
specified.\n)",
 "cause":   {
"errorType": "FileNotFoundException",
"errorMessage": "Could not load file or assembly 
'System.Net.Http.WebRequest, Version=4.0.0.0, Culture=neutral, 
  PublicKeyToken=b03f5f7f11d50a3a'. The system cannot find the file 
 specified.\n",

Here is the sample program: https://github.com/adplabs/adp-connection-NET/blob/master/ADPClientDemo/Program.cs

I can run the program on console but when I try to do it in lambda I get an error. Is it because of the NuGet from AWS?

I have the following NuGet

Amazon Lambda Core
Amazon Lambda S3 Events 
Amazon lambda Serialization json
AWS SDK Core 
Microsoft Asp Net Web Api Client 
ADP library connection NET

Answer 1

Could not load file or assembly: System.Net.Http.WebRequest

The error seems to be caused by a versioning issue, I think you need to use a .Net core version of System.Net.Http.WebRequest dll or a later version than .Net 4.0 to work with .NET Core 2.0.

Actually please see this answer you might be out of luck: The libraries you use need to ship targeting .NET Core: https://github.com/dotnet/corefx/issues/28267#issuecomment-396349873

Also see https://stackoverflow.com/a/41683787/495455 and Could not load file or assembly "System.Net.Http.Webrequest" in .NET AWSSDK for mono for similar versioning issues and fixes.

---

If that doesn't fix it, please consider using the AWS API. You could put your sample_auth.key file on an S3 bucket and read it, eg https://docs.aws.amazon.com/lambda/latest/dg/with-s3.html

---

Or as per the example you linked to they package the json file with the Lambda: https://github.com/adplabs/adp-connection-NET/tree/master/ADPClientDemo/Content/config

And they read it using StreamReader, perhaps this will work using the System.IO dll instead of trying to find the System.Net.Http.WebRequest dll:

string configFileName = "default.json";
StreamReader sr = new StreamReader("..\\..\\Content\\config\\" + configFileName);
string clientconfig = sr.ReadToEnd();