Set Lookup field using Xrm.WebAPI Javascript in dataverse power apps

When you call Create or Update methods using Xrm.WebAPI client objects, you need to take special care while setting value of lookup fields. Follow below method to do this.

Step 1 – Identify Navigation Property Name of the Lookup Column

Open the METADATA url and search the column.

The metadata url is like this https://devboxsoftchief.crm8.dynamics.com/api/data/v9.2/$metadata

you can get the Web API end point using Developer Resources from power apps screen.

From the side panel copy the Web API EndPoint.

Append $metadata to the URL and browse it.

Now search the column name to get the Navigation Property from entity metadata.

Copy the name of Navigation Property for me its fbs_CandidateId_fbs_student

Step 2 – Use navigation property in Xrm.WebAPI call

use the below code to create record.

function createAttendance(context)
{
	
	var formContext = context.getFormContext();
	var studentname = formContext.getAttribute("fbs_studentname").getValue();
	
	var studentid = formContext.data.entity.getId();
	
	// define the data to create new attendance record
		var data =
			{
				"fbs_name": "Attendance for "+ studentname,
				"fbs_CandidateId_fbs_student@odata.bind": "/fbs_students("+studentid.replace("{","").replace("}","")+")",
				"fbs_entrytime": new Date(),
				"fbs_exittime": new Date(new Date().setHours(new Date().getHours() + 8))	
			}

		// create account record
		Xrm.WebApi.createRecord("fbs_attendance", data).then(
			function success(result) {
				var alertStrings = { confirmButtonLabel: "Yes", text: "The attendance created successfully.", title: "Message" };
				var alertOptions = { height: 120, width: 260 };
				Xrm.Navigation.openAlertDialog(alertStrings, alertOptions).then(
					function (success) {
						console.log("Alert dialog closed");
					},
					function (error) {
						console.log(error.message);
					}
				);
			},
			function (error) {
				alert(error.message);
			}
		);
}

Now create web resource and attach event handler in form now it will work.

hope this helps.