错误=
SqlException：无法将值NULL插入到表“Hospitaldb.dbo. AspNetUsers”的列“PictureUrl”中;列不允许为空值。尝试失败。语句已终止。
在ImageOperation.cs文件中，

public async Task<string> ImageUpload(IFormFile file)
{
    try
    {
        if (file != null && file.Length > 0)
        {
            string fileDirectory  = Path.Combine(_env.WebRootPath, "Images");

            if (!Directory.Exists(fileDirectory ))
            {
                Directory.CreateDirectory(fileDirectory );
            }

            string filename = Guid.NewGuid().ToString() + "_" + Path.GetFileName(file.FileName);
            string filePath = Path.Combine(fileDirectory , filename);

            using (var fileStream = new FileStream(filePath, FileMode.Create))
            {
                await file.CopyToAsync(fileStream);
            }

            return filename;
        }

        return null;
    }
    catch (Exception ex)
    {
        // Log the exception
        Console.WriteLine($"Error during file upload: {ex.Message}");
        throw; 
    }
}

字符串
在身份文件中，

<div class="form-floating">
    <input type="file" name="Input.PictureUrl" class="form-control" aria-required="true" />
    <span asp-validation-for="Input.PictureUrl" class="text-danger"></span>
</div>

型
在.cs文件中，

ImageOperation image = new ImageOperation(_env);
string filename = await image.ImageUpload(Input.PictureUrl);

//if (filename == null)
//{
//    // Handle the case where image upload failed, for example, return an error to the user
//    ModelState.AddModelError(string.Empty, "Image upload failed.");
//    return Page();
//}

user.PictureUrl = filename;

型
我尝试包含string filename = Guid.NewGuid().ToString() + "_" + Path.GetFileName(file.FileName);而不是string filename = Guid.NewGuid().ToString() + "_" + file.FileName;