You should pass the file name to window.location url and do not use a single apostrophe.
$('#ui_btn_ExportCsv').click(function (event) {
var formContainer = $("#infoForm");
$.ajax({
type: 'GET',
url: '/Report/ExportReport',
data: formContainer.serialize(),
//contentType: 'application/json; charset=utf-8',
//dataType: 'json',
success: function (returnValue) {
window.location = "/Report/Download?file=" + yourFileName;
}
});
});
I believe you could get it from here:
returnValue.reportExportFile