How to get a null value if the header doesn't exist

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I am using the request context to get the value of the header called "token".

 var token = context.request.Headers.GetValues("Token")

Now If the header exists. This all works hundreds, But now if the header doesn't exist, I want it to return null. But instead it throws an exception System.InvalidOperationExecption

Is my only option to throw a try catch around it?

you can do this

if (Context.Request.Headers["Token"] != null)
{
      var token = Context.Request.Headers.GetValues("Token");         
      return token;
}
else 
      return null;

How to get a null value if the header doesn't exist, you can do this if (Context.Request.Headers["Token"] != null) { var token = Context.Request.Headers.GetValues("Token"); return token; } else return null;. Something that might clue you in that I get the same null exception in the BasePage when using variables for other things. the header section doesn't exist in the

Try using this:

 var token = string.IsNullOrEmpty(context.request.Headers.GetValues("Token")) ? null :
                               context.request.Headers.GetValues("Token");

Headers.get(), String header = null; IEnumerable<String> headerValues; if( this. The get() method of the Headers interface returns a byte string of all the values of a header within  The get() method of the Headers interface returns a byte string of all the values of a header within a Headers object with a given name. If the requested header doesn't exist in the Headers object, it returns null.

The Headers class provides a Contains() method.

Example 1:

if (!request.Headers.Contains("Token"))
    {
        return null;
    }

Example 2:

string token = request.Headers.Contains("Token") ? request.Headers.GetValues("Token").First() : null;

CLASSIC DATA STRUCTURES, 2nd ed., The get() method of the Headers interface returns a byte string of all the values of a header within a Headers object with a given name. If the requested header doesn't exist in the Headers object, it returns null . For security reasons, some headers can only be controlled by the user agent. You are trying to enumerate one header (CacheControl) instead of all the headers, which is strange. To see all the headers, use. foreach (var value in responseHeadersCollection) { Debug.WriteLine("CacheControl {0}={1}", value.Name, value.Value); } to get one specific header, convert the Headers to a dictionary and then get then one you want

You could use the Try Catch logic:

try
{
    var token = context.request.Headers.GetValues("Token");
}

catch
{
    var token = null;
}

Pro ASP.NET 3.5 Server Controls and AJAX Components, So, instead of making the data field to null value, if we store the actual data, that is, if the Input: HEADER is the pointer to the header node, KEY is the data content of the node Print “Node does not exist : Deletion is unsuccessful” 11. (iii) Find the bugs, if any, in the algorithm and then rectify it to ensure correct operation. The empty string is the only case where this would happen. I'm not sure that it's common for headers to have empty value fields (I'm not actually sure if it's even legal in HTTP, to be honest --- don't feel like studying poorly written technical documents regarding this at the moment!)

Response headers with empty values should return empty string, not , override protected void CreateChildControls() { Controls. property for a null value: if (HeaderTemplate != null) { BasicTemplateContainer header NET DataGrid control does this by rendering a simple, plain HTML table when it is bound We also add a LiteralControl object that renders a <BR> tag to make the separation. The null check for GetValues doesn't serve any value as it will never return null. If the header doesn't exist you will get an InvalidOperationException. You need to use TryGetHeaders if it's possible the header might not exist in the request and check for a false response OR try/catch around the GetValues call (not recommended).

Documentation: 9.0: COPY, If the response to a $http request contains a header but its value is empty, the value should be an empty string, not "null". Right? I get foo == null  But it’s important to understand that just because the browser has internally set an opaque origin—essentially null—that doesn’t necessarily mean the browser will send an Origin header. So see the first part of this answer for details about when browsers must send the Origin header.

Show or Hide Missing Values or Empty Rows and Columns, (An error is raised if OIDS is specified for a table that does not have OIDs, this string will be stored as a null value, so you should make sure that you use Specifies that the file contains a header line with the names of each column in the file. A ByteString representing the header's text value, or null if either the response has not yet been received or the header doesn't exist in the response. Example In this example, a request is created and sent, and a readystatechange handler is established to look for the readyState to indicate that the headers have been received; when that is

Comments
  • If Context.Request.Headers["Token"] is null and I used @token in my view, would that not throw an undefined error? Should your else not set token = null?
  • why set token to null when you can just return it as it is?
  • I'm just asking. In the question it was said "But now if the header doesn't exist, I want it to return null. But instead it throws an exception System.InvalidOperationExecption"... is that still going to happen?
  • use it like i have mentioned.
  • throwing an exception is a costly operation. Exception should be caught only in exceptional scenarios. Not in your regular code. You should avoid it as much as possible. Not a good solution.