Hi,
I have created property base64String inside EmailFormModel Class and also taken HiddenFiled on View
<%: Html.HiddenFor(model => model.Base64String, new { id = "UploadBase64" })%>
and In Javascript I have set value of it like below
var base64 = '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';
$('#image').attr("src", "data:image/png;base64," + base64);
$('#UploadBase64').val(base64);
But you have to comment above code.
I hope this will help you out.