Fix Error : A potentially dangerous Request.Form value was detected asp.net

Khi thực hiện lưu, xóa sửa dữ liệu hoặc view dữ liệu trên asp.net, c# sẽ bị lỗi như sau: A potentially dangerous Request.Form value was detected from the client

Chi tiết lỗi: Lỗi này do trong khung textbox, khung dữ liệu chứa mã html mà web cho là có nguy cơ gây nguy hiểm cho web, nên web chặn lại mỗi khi bạn request dữ liệu.

Cách sử lỗi: chuyển requestValidationMode thành 2.0 để vượt qua lỗi này bằng cách

• Khai bào vào trong web.config thêm đoạn code <httpRuntime requestValidationMode="2.0" /> và <pages validateRequest="false" /> trong thẻ <system.web> như dưới.
• Lưu lại là xong.

Mã:

<configuration>
...
      <location path="MyFolder/.aspx">
      <system.web>
      <pages validateRequest="false" />
      <httpRuntime requestValidationMode="2.0" />
      </system.web>
      </location>
...
</configuration>

Chi tiết lỗi:

Mã:

Server Error in '/' Application.
A potentially dangerous Request.Form value was detected from the client (ctl00$ContentPlaceHolder1$txtDescription="...n da mịn màng, căng b&#24...").
Description: ASP.NET has detected data in the request that is potentially dangerous because it might include HTML markup or script. The data might represent an attempt to compromise the security of your application, such as a cross-site scripting attack. If this type of input is appropriate in your application, you can include code in a web page to explicitly allow it. For more information, see http://go.microsoft.com/fwlink/?LinkID=212874.
Exception Details: System.Web.HttpRequestValidationException: A potentially dangerous Request.Form value was detected from the client (ctl00$ContentPlaceHolder1$txtDescription="...n da mịn màng, căng b&#24...").
Source Error:
[No relevant source lines]
Source File: c:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root\1fbe6c70\38f3f5c8\App_Web_getautolinknews.aspx.be00b3d8.xiiij_ai.0.cs    Line: 0
Stack Trace:
[HttpRequestValidationException (0x80004005): A potentially dangerous Request.Form value was detected from the client (ctl00$ContentPlaceHolder1$txtDescription="...n da mịn màng, căng b&#24...").]
   System.Web.HttpRequest.ValidateString(String value, String collectionKey, RequestValidationSource requestCollection) +9777772
   System.Web.HttpRequest.ValidateHttpValueCollection(HttpValueCollection collection, RequestValidationSource requestCollection) +194
   System.Web.HttpRequest.get_Form() +50
   System.Web.HttpRequest.get_HasForm() +9778063
   System.Web.UI.Page.GetCollectionBasedOnMethod(Boolean dontReturnNull) +95
   System.Web.UI.Page.DeterminePostBackMode() +69
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +6605
   System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +279
   System.Web.UI.Page.ProcessRequest() +72
   System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context) +22
   System.Web.UI.Page.ProcessRequest(HttpContext context) +58
   ASP.admincp_getautolinknews_aspx.ProcessRequest(HttpContext context) in c:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files\root\1fbe6c70\38f3f5c8\App_Web_getautolinknews.aspx.be00b3d8.xiiij_ai.0.cs:0
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +188
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +69
Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.6.81.0