A potentially dangerous Request.Path value was detected from the client (*)

If you're using .NET 4.0 you should be able to allow these urls via the web.config

<system.web>
    <httpRuntime 
            requestPathInvalidCharacters="&lt;,&gt;,%,&amp;,:,\,?" />
</system.web>

Note, I've just removed the asterisk (*), the original default string is:

<httpRuntime 
          requestPathInvalidCharacters="&lt;,&gt;,*,%,&amp;,:,\,?" />

See this question for more details.

The * character is not allowed in the path of the URL, but there is no problem using it in the query string:

http://localhost:3286/Search/?q=test*

It's not an encoding issue, the * character has no special meaning in an URL, so it doesn't matter if you URL encode it or not. You would need to encode it using a different scheme, and then decode it.

For example using an arbitrary character as escape character:

query = query.Replace("x", "xxx").Replace("y", "xxy").Replace("*", "xyy");

And decoding:

query = query.Replace("xyy", "*").Replace("xxy", "y").Replace("xxx", "x");

For me, I am working on .net 4.5.2 with web api 2.0, I have the same error, i set it just by adding requestPathInvalidCharacters="" in the requestPathInvalidCharacters you have to set not allowed characters else you have to remove characters that cause this problem.

<system.web>
     <httpRuntime targetFramework="4.5.2" requestPathInvalidCharacters="" />
     <pages  >
      <namespaces>
     ....
 </namespaces>
    </pages> 
  </system.web>

**Note that it is not a good practice, may be a post with this parameter as attribute of an object is better or try to encode the special character. -- After searching on best practice for designing rest api, i found that in search, sort and paginnation, we have to handle the query parameter like this

/companies?search=Digital%26Mckinsey

and this solve the problem when we encode & and remplace it on the url by %26 any way, on the server we receive the correct parameter Digital&Mckinsey

this link may help on best practice of designing rest web api https://hackernoon.com/restful-api-designing-guidelines-the-best-practices-60e1d954e7c9

You should encode the route value and then (if required) decode the value before searching.

For me, when typing the url, a user accidentally used a / instead of a ? to start the query parameters

e.g.:

url.com/endpoint/parameter=SomeValue&otherparameter=Another+value

which should have been:

url.com/endpoint?parameter=SomeValue&otherparameter=Another+value

This exception occurred in my application and was rather misleading.

It was thrown when I was calling an .aspx page Web Method using an ajax method call, passing a JSON array object. The Web Page method signature contained an array of a strongly-typed .NET object, OrderDetails. The Actual_Qty property was defined as an int, and the JSON object Actual_Qty property contained "4 " (extra space character). After removing the extra space, the conversion was made possible, the Web Page method was successfully reached by the ajax call.

Try to set web project's server propery as Local IIS if it is IIS Express. Be sure if project url is right and create virual directory.

When dealing with Uniform Resource Locator(URL) s there are certain syntax standards, in this particular situation we are dealing with Reserved Characters.

As up to RFC 3986, Reserved Characters may (or may not) be defined as delimiters by the generic syntax, by each scheme-specific syntax, or by the implementation-specific syntax of a URI's dereferencing algorithm; And asterisk(*) is a Reserved Character.

The best practice is to use Unreserved Characters in URLs or you can try encoding it.

Keep digging :

HTML URL Encoding Reference (w3schools)

When to Encode or Decode (RFC 3986)

I had a similar issue in Azure Data Factory with the : character.

I resolved the problem by substituting : with %3A

as shown here.

For example, I substituted

date1=2020-01-25T00:00:00.000Z

with

date1=2020-01-25T00%3A00%3A00.000Z