c# - 如何在不单击保存按钮的情况下将图像上传到页面，同时避免在 asp.net 中刷新

Question

实际上，我正在使用控件来上传两个图像，但我想通过单击浏览按钮而不单击保存按钮来更改图像我希望浏览的图像稳定，但是在选择任何下拉方式时它会消失，而页面刷新它会消失？我正在使用以下代码：

<input type="file" id="files" name="files[]" multiple />
<output id="list"></output>
        <!-- Place updatable markup and controls here. -->
<script>
    function handleFileSelect(evt) {
        var files = evt.target.files; // FileList object

        // Loop through the FileList and render image files as thumbnails.
        for (var i = 0, f; f = files[i]; i++) {

            // Only process image files.
            if (!f.type.match('image.*')) {
                continue;
            }

            var reader = new FileReader();

            // Closure to capture the file information.
            reader.onload = (function (theFile) {
                return function (e) {
                    // Render thumbnail.
                    var span = document.createElement('span');
                    span.innerHTML = ['<img class="thumb" src="', e.target.result,
                            '" title="', escape(theFile.name), '"/>'].join('');
                    document.getElementById('list').insertBefore(span, null);
                };
            })(f);

            // Read in the image file as a data URL.
            reader.readAsDataURL(f);
        }
    }

    document.getElementById('files').addEventListener('change', handleFileSelect, false);
</script>