(VB.NET) Download Photo to a File

Assuming we have the ID of a Photo, this example demonstrates how to download the photo image data to a file.

Chilkat .NET Downloads Chilkat .NET Framework Chilkat for .NET Core

' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

' This example assumes a previously obtained an access token
Dim oauth2 As New Chilkat.OAuth2
oauth2.AccessToken = "FACEBOOK-ACCESS-TOKEN"

Dim rest As New Chilkat.Rest

' Connect to Facebook...
Dim success As Boolean = rest.Connect("graph.facebook.com",443,True,True)
If (success <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


' Provide the authentication credentials (i.e. the access key)
rest.SetAuthOAuth2(oauth2)

' Assumes we've already obtained a Photo ID.
Dim photoId As String = "10210199026347451"

Dim sbPath As New Chilkat.StringBuilder
sbPath.Append("/v2.7/")
sbPath.Append(photoId)

' First we're going to get the photo informaton so we can get the URL of the image file data.
' Select the fields we want.
' See https://developers.facebook.com/docs/graph-api/reference/photo/
rest.AddQueryParam("fields","id,album,images")

Dim responseJson As String = rest.FullRequestNoBody("GET",sbPath.GetAsString())
If (rest.LastMethodSuccess <> True) Then
    Debug.WriteLine(rest.LastErrorText)
    Exit Sub
End If


Dim json As New Chilkat.JsonObject
json.EmitCompact = False
json.Load(responseJson)

' Show the JSON in human-readable format.
Debug.WriteLine(json.Emit())

' Get the image URL.
Dim imageUrl As String = json.StringOf("images[0].source")
Debug.WriteLine("Downloading from " & imageUrl)

Dim sbImageUrl As New Chilkat.StringBuilder
sbImageUrl.Append(imageUrl)

' Build the output local file path.
Dim sbToPath As New Chilkat.StringBuilder
sbToPath.Append("qa_output/fb")
sbToPath.Append(json.StringOf("id"))
Dim bCaseSensitive As Boolean = False
If (sbImageUrl.Contains(".jpg",bCaseSensitive) = True) Then
    sbToPath.Append(".jpg")
Else
    sbToPath.Append(".png")
End If

Debug.WriteLine("Downloading to " & sbToPath.GetAsString())

' Download using Chilkat HTTP.
Dim http As New Chilkat.Http
success = http.Download(imageUrl,sbToPath.GetAsString())
If (success <> True) Then
    Debug.WriteLine(http.LastErrorText)
Else
    Debug.WriteLine("Downloaded.")
End If