System.Web.HttpException: Validation of viewstate MAC failed解决方法!

Server Error in '/ ' Application.
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Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Web.HttpException: Validation of viewstate MAC failed. If this application is hosted by a Web Farm or cluster, ensure that <machineKey> configuration specifies the same validationKey and validation algorithm. AutoGenerate cannot be used in a cluster.

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提交的内容太多了，超过了web.config中定义的最大上传字节量。
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在Web.config里边添加 <pages enableEventValidation= "false " viewStateEncryptionMode = "Never " />