React-Native WebView: Issue downloading and saving dynamically generated file - react-native

Question

We are opening a Url (in WebView) which has a button that dynamically generates and downloads a file (e.g. PDF or Excel or any other type) based on user selected filters. This means that we do not have direct link to those files which can be downloaded using network request. In chrome, we can see downloaded file. However in WebView, we neither see download file (the way chrome shows at the bottom of window) nor we get any way to intercept/view the location where it is downloaded silently. Below is webview:
<WebView
ref={ref => (webview = ref)}
originWhitelist={['*']}
source={{ uri: pageURL }}
javaScriptEnabled={true}
startInLoadingState={true}
scalesPageToFit={true}
domStorageEnabled={true}
onError={(err) => console.log(err)}
onHttpError={(err) => console.log(err)}
allowFileAccess={true}
allowFileAccessFromFileURLs={true}
allowUniversalAccessFromFileURLs={true}
allowingReadAccessToURL={true}
mixedContentMode="always"
onFileDownload={({ nativeEvent }) => {
const { downloadUrl } = nativeEvent;
console.log(downloadUrl);
}}
onNavigationStateChange={handleWebViewNavigationStateChange}
onLoad={() => {
webview.injectJavaScript(jsCode);
}}
onMessage={event => {
const { data } = event.nativeEvent;
}}
/>
So, we have below queries:
How to know if WebView actually downloaded a file?
Is there a way to know where WebView downloads a file?
Is there a way to specify default location where WebView should download a file?
Environment:
Expo: 40.0.0,
React-native: 0.63,
react-native-webview: 11.0.0
We clicked on "Allow" when it asked for permission to download and store file on device. Also, onNavigationStateChange is not firing when button is clicked (may be because the file is downloaded on same page without navigating). We have onError and onHttpError which does not print anything so there does not seem to be any issue there.
Below is the code (C#) that gets executed when button is clicked to download file:
string attachment = "attachment; filename=temp.csv";
HttpContext.Current.Response.Clear();
HttpContext.Current.Response.ClearHeaders();
HttpContext.Current.Response.ClearContent();
HttpContext.Current.Response.AddHeader("content-disposition", attachment);
HttpContext.Current.Response.ContentType = "text/csv";
HttpContext.Current.Response.AddHeader("Pragma", "public");
// Prepare file content
HttpContext.Current.Response.Write(fileContent.ToString());
HttpContext.Current.Response.Flush();
HttpContext.Current.Response.Close();