¿如何从 xamarin 表单 Android 中的 MultipartFormDataContent 中删除图像？

Question

我在C#Xamarin Forms Android 中使用此代码

MultipartFormDataContent content = new MultipartFormDataContent();
private async void Scanner()
{
var scannerPage = new ZXingScannerPage();
scannerPage.Title = "scanner";
scannerPage.OnScanResult += (result) =>
{
scannerPage.IsScanning = false;
string resultado = Convert.ToString(result);
if (resultado.Contains("http") || resultado.Contains("https"))
{
Browser.OpenAsync(resultado, BrowserLaunchMode.External);
Navigation.PopAsync();
}
else
Device.BeginInvokeOnMainThread(async () =>
{
Navigation.PopAsync();
//Hace el display del valor obtenido
subs = result.Text.Split('t');
string cadena = "var1N°: " + subs[0] + "nvar2 N°: " + subs[1] + "nvar3 N°: " + subs[2];
await this.DisplayAlert("Datos del QR", cadena, "OK");
sacarFotos();
});
};
await Navigation.PushAsync(scannerPage);

}
private async Task<bool> GetResultFromAlert()
{
return await this.DisplayAlert("Test", "Message", "Ok", "Cancel");
}
private Task DisplayAlert(string v1, string v2)
{
throw new NotImplementedException();
}
private async void TakePhotos()
{
var file2 = await MediaPicker.CapturePhotoAsync();

while (file2 != null)
{
Image im = new Image();
im.ClassId = contador.ToString();
im.Source = ImageSource.FromFile(file2.FullPath);
im.HeightRequest = 600;
im.WidthRequest = 600;
im.MinimumHeightRequest = 600;
im.MinimumWidthRequest = 600;
im.VerticalOptions = LayoutOptions.End;
im.HorizontalOptions = LayoutOptions.End;
im.Aspect = Aspect.AspectFill;
imgs.Children.Add(im);
Button deleteButton = new Button();
deleteButton.Text = "Delete image";
deleteButton.VerticalOptions = LayoutOptions.CenterAndExpand;
deleteButton.HorizontalOptions = LayoutOptions.Center;
deleteButton.MinimumWidthRequest = 100;
deleteButton.ClassId = contador.ToString();
deleteButton.Clicked += async (sender, args) => {
imgs.Children.Remove(im);
imgs.Children.Remove(deleteButton);
};
imgs.Children.Add(deleteButton);

content.Add(new StreamContent(await file2.OpenReadAsync()), "file", subs[0] + "_" + subs[1] + "_" + subs[2] + "_" + contador + "_" + file2.FileName);

file2 = await MediaPicker.CapturePhotoAsync();

contador++;
}

btnScannerQR.IsVisible = false;
btnSacarFotos.IsVisible = true;
btnEnviarImagenes.IsVisible = true;
}
private async void enviarFotos()
{
bool answer = await DisplayAlert("¿Have you finished?", "¿are you sure you want to send the images?", "Yes", "No"); 

if(answer)
{
//////////////////////////////////////////
/// algorithm to remove deleted images ///
//////////////////////////////////////////
var httpClient = new HttpClient();
var response = await httpClient.PostAsync("url", content);
string res = await response.Content.ReadAsStringAsync();
await DisplayAlert("Result", res, "OK");
btnSacarFotos.IsVisible = false;
btnEnviarImagenes.IsVisible = false;
btnScannerQR.IsVisible = true;
content = null;
imgs.Children.Clear();
Shell.Current.GoToAsync($"//{nameof(HomePage)}");
}
else
{
// lblStatus.Text = "Nothing sent";
}

因此，我动态地创建图像和按钮，也可以将它们从显示器中删除，但当用户发送图像时，我无法将其从MultipartFormDataContent中删除。有人知道如何从MultipartFormDataContent中删除图像？非常感谢。

Answer 1

解决方案

好吧，基本上我在发送图像之前添加了所有内容。我把代码留在这里。也许可以帮助别人。

string[] subs;
MultipartFormDataContent content = new MultipartFormDataContent();
MultipartFormDataContent content2 = new MultipartFormDataContent();
List<StreamContent> listStreamContent = new List<StreamContent>();
List<string> listImgName = new List<string>();
List<string> ControlCantName = new List<string>();
List<int> listDelete = new List<int>();
private async void TakePhotos()
{
try
{
bool answer = await DisplayAlert("¿Have you finished?", "¿are you sure", "Yes", "No"); 
if(answer)
{
int contImgBorradas;
if (listDelete.Count > 0 || listDelete != null)
{
foreach (var num in listDelete)
{
contImgBorradas = 1;
foreach (var img in ControlCantName)
{
if (num == contImgBorradas)
{
listImgName.Remove(num - 1);
listStreamContent.Remove(num - 1);
}
contImgBorradas++;
}
}
}
for (int x = 0; x < listStreamContent.Count; x++)
{
content2.Add(listStreamContent[x], "file", listImgName[x]);
}
var httpClient = new HttpClient();
var response = await httpClient.PostAsync("url", content2);
// lblStatus.Text = await response.Content.ReadAsStringAsync();
string res = await response.Content.ReadAsStringAsync();
await DisplayAlert("Resultado", res, "OK");
btnSacarFotos.IsVisible = false;
btnEnviarImagenes.IsVisible = false;
btnScannerQR.IsVisible = true;
content = null;
content2 = null;
imgs.Children.Clear();
await Shell.Current.GoToAsync($"//{nameof(HomePage)}");

}
}
catch(Exception ex)
{
await DisplayAlert("Error", "sorry, we had a problem. Try again.", "OK");
await Shell.Current.GoToAsync($"//{nameof(HomePage)}");
}
}