Adding custom properties for each request in Application Insights metrics

Question

I d\'like to add custom properties to metrics taken by Application Insights to each request of my app. For example, I want to add the user login and the ten

Answer 1

You can use the static HttpContext.Current's Items dictionary as a short term (near stateless) storage space to deliver your custom property values into the default telemetry handler with a custom ITelemetryInitializer

Implement handler

class AppInsightCustomProps : ITelemetryInitializer
{
    public void Initialize(ITelemetry telemetry)
    {
        var requestTelemetry = telemetry as RequestTelemetry;
        // Is this a TrackRequest() ?
        if (requestTelemetry == null) return;

        var httpCtx = HttpContext.Current;
        if (httpCtx != null)
        {
            var customPropVal = (string)httpCtx.Items["PerRequestMyCustomProp"];
            if (!string.IsNullOrWhiteSpace(customPropVal))
            {
                requestTelemetry.Properties["MyCustomProp"] = customPropVal;
            }
        }
    }
}

Hook it in. Put this inside Application_Start in global.asax.cs

TelemetryConfiguration.Active.TelemetryInitializers.Add(new AppInsightCustomProps());

Program the desired custom property, anywhere in your request pipeline have something like

if (HttpContext.Current != null)
{
    HttpContext.Current.Items["PerRequestMyCustomProp"] = myCustomPropValue;
}