Read and Download Response from URL using C# .Net

Hi slb2013,

Here I have created sample that full-fill your requirement.

HTML

<div>
    Enter Id Number : <asp:TextBox runat="server" ID="TextNumber"></asp:TextBox>&nbsp;&nbsp;
    <asp:Button ID="btnSAS" Text="SAS" runat="server" OnClick="BtnSAS_Click" />
</div>

C#

protected void BtnSAS_Click(object sender, EventArgs e)
{
    string IdNumber = TextNumber.Text.Trim();
    string UrlA = "https://microsoft-apiapp80ce5187f0b2490aadbc980673a5485d.azurewebsites.net/api/GetBlobs/Blob?blobContainer=12062&blobName=" + IdNumber + ".pdf&passKey=RecorderAz4ass3ey";
    string UrlB = ResFromServer(UrlA);
    ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "Key", "NewWindow=window.open('" + UrlB + "','PDFViewer','menubar=0, location=1, toolbars=1, scrollbars= 1, resizable=1, width=750,height=775, top=150, left=220')", true);
}

public string ResFromServer(string url)
{
    string location = string.Copy(url);
    string responseFromServer = string.Empty;
    if (!string.IsNullOrEmpty(location))
    {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create(location);
        request.AllowAutoRedirect = false;
        using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
        {
            Stream dataStream;
            dataStream = response.GetResponseStream();
            StreamReader reader = new StreamReader(dataStream);
            responseFromServer = reader.ReadToEnd();
        }
    }
    return responseFromServer;
}

Screenshot