What is the error message in Blazor?

        try

        {

            var ret = await Http.GetFromJsonAsync<string>(url);

            if (ret?.Length > 0)

            {

                rest = ret;

            }

        }

        catch (Exception E)

        {

            error = E.Message;

        }

E.Message means: TypeError: Failed to fetch 

Are you sure it is returning a Json response?  It would also error out if it wasn't able to parse the response as Json.

While troubleshooting, maybe try something along the lines of

var response = await Http.GetAsync(url);

if(response.IsSuccessStatusCode)
	ret = await response.Content.ReadFromJsonAsync<string>();

And set a breakpoint at the response line or log it in some way to see what the full response is that you're receiving.

It crashes in : var response = await Http.GetAsync(url);

response has value null

Did you allow it to step to the next line after the response? It shouldn't be null if you're hitting a valid url/endpoint. The debugger will say it's null until you step to the next line after it.

Your comments are very helpfuil.

I build a CoreWebAPI Restservice. He has two Adresses

1. Http:
2. Https

If i used your code on the http Rest there is a crash GetTaSYNC89 and I´m in the Exception Clause.

If I used the http Adress, i get a string not a String in Json. and so it is not possible to convert  from Json to string,.

==> I will now ensure that i get a Jason Object  in my test Software. In my Legacy sotware i have it fixed that is a Json covered string.

==> Is it not allowed to consume a http Rest ? 

==> Is there any Method/Switch to allow http Rest to use ?

==> Especially in Legacy systems I have often only http Rest Services.

Thank you for your support and advice.

This link may be helpful: https://docs.microsoft.com/en-us/aspnet/core/blazor/call-web-api?view=aspnetcore-5.0&pivots=webassembly

I believe that it is not possible to access a REST Service with http://.

If your non-secure Blazor site isn't able to work with your API, then maybe your API isn't setup to allow non-secure traffic? Are you either redirecting all non-secure URL's to a secure URL, or maybe haven't setup your API Authentication to not require https metadata?

The first two thoughts that come to mind for common setups is to:

1. Check whether you have "app.UseHttpsRedirection()" in your Configure method of your Startup.cs file.  This would force a redirect.
2. If you're using JWT Bearer Tokens, when you setup something like "services.AddAuthentication().AddJwtBearer()" in Startup.cs, make sure you set options.RequireHttpsMetaData = false. See a general example below

services.AddAuthentication()
	.AddJwtBearer(IdentityServerJwtConstants.IdentityServerJwtBearerScheme, options =>
	{
		...
		options.RequireHttpsMetadata = false;
		...
	});