How to use the TempData attribute to pass data to a Razor view - asp.net-core

Question

I have:
namespace Test
{
public interface ITest
{
public string Test1(string s);
}
public class Test : ITest
{
[Microsoft.AspNetCore.Mvc.TempData]
public string Message
{
get; set;
}
public string Test1(string s)
{
Message = "Test " + s;
return "Test has run";
}
}
}
And in Startup.cs:
services.AddScoped<Test.ITest, Test.Test>();
Then in a Razor view:
#inject Test.ITest Test
<p>Result is #Test.Test1("Hello World!")</p>
<p>TempData["Message"] is #TempData["Message"]</p>
The output is:
Result is Test has run
TempData["Message"] is
Where have I done incorrectly? How can I pass a TempData["Message"] from some code (that is not in a Controller) to a Razor page?

Answer 1

How can I pass a TempData["Message"] from some code (that is not in a Controller) to a Razor page?
If you'd like to retain and pass value via TempData inside your custom service, you can try the following code snippet.
public interface ITest
{
public string Test1(string s);
public string Test2();
}
public class Test : ITest
{
private readonly IHttpContextAccessor _httpContextAccessor;
public Test(IHttpContextAccessor httpContextAccessor)
{
_httpContextAccessor = httpContextAccessor;
}
public string Message
{
get {
var tempDataDictionaryFactory = _httpContextAccessor.HttpContext.RequestServices.GetRequiredService<ITempDataDictionaryFactory>();
var tempDataDictionary = tempDataDictionaryFactory.GetTempData(_httpContextAccessor.HttpContext);
if (tempDataDictionary.TryGetValue("Message", out object value))
{
return (string)value;
};
return "";
}
set
{
var tempDataDictionaryFactory = _httpContextAccessor.HttpContext.RequestServices.GetRequiredService<ITempDataDictionaryFactory>();
var tempDataDictionary = tempDataDictionaryFactory.GetTempData(_httpContextAccessor.HttpContext);
tempDataDictionary.Remove("Message");
tempDataDictionary.TryAdd("Message", value);
}
}
public string Test1(string s)
{
Message = "Test " + s;
return "Test has run";
}
public string Test2()
{
return Message;
}
}
In Razor Page
<p>Result is #Test.Test1("Hello World!")</p>
<p>TempData["Message"] is #TempData.Peek("Message")</p>
<p>#Test.Test2()</p>
Test Result