Dataverse: Create GetLastDateOfMonth Function in Custom Connector

Do you know we can write Code (Preview) in Custom Connector? In this blog post, we will make a simple function that will return the last date of the month to try the feature. Without further ado here are the steps:

Go to > Dataverse Custom Connectors > on the top right hit + New custom connector > Create from blank option:

Create Blank Custom Connector

Then we need to fill in the General Information below:

General tab

I put the host as This Host URL will be replaced automatically. So you can put any URL that you want.

The next is the Security tab. Here I am following the official documentation which uses API Key:

Security tab

In the Definition tab, you can create the Action/API Method that you want to create. For this example, I named it as GetlastDateOfMonth. Once you define the action, you need to define the Request and Response also.


Here is my Request (asking for parameter date):


Then for the Response, I design that the API can return two properties (Result and Error):


The Response Sample:

  "Result": "4/9/2022",
  "Error": "Error"

And here is the fun part! Where we need to create the code. For now, I don’t know how we can write the code efficiently. But when I wrote this code, I depends on the sample that was being generated automatically and in this GitHub code

public class Script : ScriptBase
    public override async Task<HttpResponseMessage> ExecuteAsync()
		var query = HttpUtility.ParseQueryString(this.Context.Request.RequestUri.Query);
		var inputDateString = query.Get("date");
		if(string.IsNullOrEmpty(inputDateString)) return CreateHttpResponseMessage(HttpStatusCode.BadRequest, 
			"{\"Error\": \"Date QueryString is empty.\"}");
        if (!DateTime.TryParse(inputDateString, out DateTime inputDate))
			return CreateHttpResponseMessage(HttpStatusCode.BadRequest, 
				"{\"Error\": \"Bad Format\"}");
		var lastDay = DateTime.DaysInMonth(inputDate.Year, inputDate.Month);
		var lastDayOfTheMonth = new DateTime(inputDate.Year, inputDate.Month, lastDay);
		return CreateHttpResponseMessage(HttpStatusCode.OK, "{\"Result\": \"" + lastDayOfTheMonth.ToShortDateString() + "\"}");
	private HttpResponseMessage CreateHttpResponseMessage(HttpStatusCode statusCode, string content)
		return new HttpResponseMessage(statusCode)
			Content = CreateJsonContent(content)

Then you need to check the Code Enabled and paste the code above, create the Connector and the last part was to create Connection.

The code 😁

Once you did it, you can test it from the page. But the Test functionality will automatically encode the input. So in the end I tested it using Postman with the below request:

Success Result

Here is the result if we don’t put the date QueryString:

Validation 1

And the last one if we put the wrong date string:

Validation 2

You also need to read the FAQ for the supported namespace (still limited and still got lots of improvement here).

Happy CRM-ing!


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