Web.config添加如下代码：

<system.web>
    <httpRuntime  maxRequestLength="1048567" executionTimeout="3600" />

    ...
</system.web>

<system.webServer>
    <security>
        <requestFiltering>
            <requestLimits maxAllowedContentLength="1048567" />
        </requestFiltering>
    </security>

    ...
</system.webServer>

ajax上传大附件报错：413 Request Entity Too Large