Update IformFile

Question

I have a requirement to read an excel file from the system and to modify that file (eg remove duplicates ) and drop it in to another location. I am using IFormFile.

Can anyone help me to remove duplicates from the file and update the same file and create a new file with the duplicated values.

Here is what I have to read the file

var result = new StringBuilder();
using (var reader = new StreamReader(iFormFile.OpenReadStream()))
{
  //read till EOF
  while (reader.Peek() >= 0) 
  {
      result.AppendLine(await reader.ReadLineAsync());
  }
}


 public async Task<Stream> ValidateDataFileAsync(Stream stream, CancellationToken token)
    {
        List<string> result = new List<string>();
        using (var reader = new StreamReader(stream))
        {
            while (reader.Peek() >= 0)
           result.Add(await reader.ReadLineAsync());
        }

        HashSet<string> hSet = new HashSet<string>(result);
       return hSet;

//How do i convert the hashset to stream.

    }

Answer 1

Firstly install the Nuget:

Install-Package WindowsAzure.Storage -Version 9.3.3

and

Install-Package EPPlus -Version 4.5.2.1

Make an interface IBlobManager.cs which will house all your Blob operations:

using System;
using System.IO;
using System.Threading.Tasks;

namespace UploadAzureBlob.Services
{
    public interface IBlobManager
    {
        Task<string> UploadFileToBlobAsync(string fileName, Stream stream);
    }
}

Implement the above interface in a class BlobManager.cs:

using Microsoft.WindowsAzure.Storage;
using Microsoft.WindowsAzure.Storage.Blob;
using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Threading.Tasks;

namespace UploadAzureBlob.Services
{
    public class BlobManager : IBlobManager
    {
        private CloudBlobClient cloudBlobClient;
        public BlobManager()
        {
            // Retrieve the connection string for blob storage
            string storageConnectionString = "";

            CloudStorageAccount.TryParse(storageConnectionString, out CloudStorageAccount storageAccount);

            // Create the CloudBlobClient that represents the Blob storage endpoint for the storage account.
            cloudBlobClient = storageAccount.CreateCloudBlobClient();
        }

        /// <summary>
        /// Uploads a file to blob storage.
        /// </summary>
        /// <param name="fileName"></param>
        /// <param name="file"></param>
        /// <returns></returns>
        public async Task<string> UploadFileToBlobAsync(string fileName, Stream stream)
        {
            try
            {
                // Create a container.
                CloudBlobContainer blobContainer = cloudBlobClient.GetContainerReference("test");
                await blobContainer.CreateAsync();

                BlobContainerPermissions perm = await blobContainer.GetPermissionsAsync();
                perm.PublicAccess = BlobContainerPublicAccessType.Container;
                await blobContainer.SetPermissionsAsync(perm);

                // Get a reference to the blob address, then upload the file to the blob.
                var cloudBlockBlob = blobContainer.GetBlockBlobReference(fileName);
                await cloudBlockBlob.UploadFromStreamAsync(stream);

                // Returning the URI of the freshly created resource
                return cloudBlockBlob.Uri.ToString();
            }
            catch (StorageException ex)
            {
                throw;
            }
        }
    }
}

Now finally in your controller:

public async Task<string> ValidateDataFileAsync(IFormFile formFile)
{
        List<string> result = new List<string>();

        using (var reader = new StreamReader(formFile.OpenReadStream()))
        {
            //read till EOF
            while (reader.Peek() >= 0)
                result.Add(reader.ReadLineAsync().Result);
        }

        // Filter by repeated items
        result = result.GroupBy(x => x).Where(x => x.Count() > 1).Select(x => x.Key).ToList();

        // Write the List<string> into the MemoryStream using the EPPlus package

        MemoryStream memoryStream = new MemoryStream();
        using (var package = new ExcelPackage())
        {
            var worksheet = package.Workbook.Worksheets.Add("Worksheet 1");
            worksheet.Cells["A1"].LoadFromCollection(result);
            memoryStream = new MemoryStream(package.GetAsByteArray());
        }

        IBlobManager blobManager = new BlobManager();
        string newResourceUri = await blobManager.UploadFileToBlobAsync(formFile.FileName, memoryStream);
        return newResourceUri;
}