Code to save attachement file format in database using .net core

try this,

public class FileModel
{
    public int Id { get; set; }
    public string FileName { get; set; }
    public string ContentType { get; set; }
    public byte[] Data { get; set; }
}

[Route("api/files")]
[ApiController]
public class FileController : ControllerBase
{
    private readonly ApplicationDbContext _context;

    public FileController(ApplicationDbContext context)
    {
        _context = context;
    }

    [HttpPost]
    [Route("upload")]
    public async Task UploadFile(IFormFile file)
    {
        if (file == null || file.Length <= 0)
        {
            return BadRequest("Invalid file");
        }

        using (var memoryStream = new MemoryStream())
        {
            await file.CopyToAsync(memoryStream);
            var fileData = memoryStream.ToArray();

            var fileModel = new FileModel
            {
                FileName = file.FileName,
                ContentType = file.ContentType,
                Data = fileData
            };

            _context.FileModels.Add(fileModel);
            await _context.SaveChangesAsync();

            return Ok(new { fileId = fileModel.Id });
        }
    }
}

Angular

import { Component } from '@angular/core';
import { HttpClient } from '@angular/common/http';

@Component({
  selector: 'app-file-upload',
  templateUrl: './file-upload.component.html'
})
export class FileUploadComponent {
  selectedFile: File | null = null;

  constructor(private http: HttpClient) { }

  onFileSelected(event: any) {
    this.selectedFile = event.target.files[0];
  }

  uploadFile() {
    if (!this.selectedFile) {
      console.error('Please select a file.');
      return;
    }

    const formData = new FormData();
    formData.append('file', this.selectedFile);

    this.http.post('/api/files/upload', formData).subscribe(
      (response: any) => {
        console.log('File uploaded successfully. File ID:', response.fileId);
        // Handle success, e.g., display a success message
      },
      (error) => {
        console.error('Error uploading file:', error);
        // Handle error, e.g., display an error message
      }
    );
  }
}