说明：先传递三个List，后台接收后做一些处理，然后回传字符串，将字符串写入文件，生成下载文件，自动下载。

前端：

@{
// 定义
List<int> cstarts = new List<int>() { 1, 2, 3};
List<int> cends = new List<int>() { 4, 5, 6 };
List<string> cstrs = new List<string>() { "", "sss", "x"};
}

<!-- html内容略 -->

<button id="exportSeqBtn" onclick="exportSeq()" type="button">
    导出序列
</button>

<!-- js -->
<script>
    // 导出序列
    function exportSeq() {
        var starts = @Html.Raw(Json.Encode(cstarts));
        var ends = @Html.Raw(Json.Encode(cends));
        var strs = @Html.Raw(Json.Encode(cstrs));
        $.ajax({
            url: "/Home/ExportSeq",
            method: 'POST',
            data: JSON.stringify({
                vid: @Model.Id,
                cstarts: starts,
                cends: ends,
                cstrs: strs,
            }),
            contentType: 'application/json; charset=utf-8',
            success: function (data) {
                var blob = new Blob([data], { type: 'text/plain' });
                var link = document.createElement('a');
                link.href = window.URL.createObjectURL(blob);
                link.download = 'sequence.fa'; // 下载文件的文件名
                link.click();
            },
            error: function (xhr, status, error) {
                alert('An error occurred while generating the file: ' + error);
            }
        });
    }
</script>

后端：

[HttpPost]
public ActionResult ExportSeq(string vid, List<int> cstarts, List<int> cends, List<string> cstrs) {
	var txtContent = new StringBuilder();
    // do something
    txtContent.AppendLine(string.Join(",", cstarts));
    // 可以打印其他的看看
    return Content(txtContent.ToString(), "text/plain");
}