Work with Excel file using Sharepoint document library with Microsoft Graph API

I downloaded and customized this project asp mvc todo sample. this is working fine without any issue with onedrive excel files/items. but i have to do this using office 365 sharepoint online only. i am able to get file id using service point as follows:

var serviceEndpoint = "https://graph.microsoft.com/beta/sites/mydomain.sharepoint.com:/foa/bd:/lists/Budget/items";

But I am not sure how should I define workbook end point URL with Sharepoint to update/manipulate same excel file data. Current workbook end point URL as follows (which is not working):

var workbookEndpoint = "https://graph.microsoft.com/beta/sites/mydomain.sharepoint.com:/foa/bd:/lists/Budget/items/" + fileId + "/workbook";

My complete method to update cell value in excel file on Sharepoint as follows:

public static async Task UpdateExcelCellValue_Sharepoint(string accessToken, string cellAddress, string val)
    {
        string worksheetName = "Parameters";
        var serviceEndpoint = "https://graph.microsoft.com/beta/sites/mydomain.sharepoint.com:/foa/bd:/lists/Budget/items";
        HttpClient client = new HttpClient();
        client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);
        var filesResponse = await client.GetAsync(serviceEndpoint + "?$select=name,id");
        if (filesResponse.IsSuccessStatusCode)
        {
            var filesContent = await filesResponse.Content.ReadAsStringAsync();
            JObject parsedResult = JObject.Parse(filesContent);
            foreach (JObject file in parsedResult["value"])
            {
                var name = (string)file["id"];
                if (name.Contains("173"))
                {
                    fileId = (string)file["id"];
                    break;
                }
            }
        }
        else
        {
            //Handle failed response
        }
        //Set up workbook and worksheet endpoints
        var workbookEndpoint = "https://graph.microsoft.com/beta/sites/mydomain.sharepoint.com:/foa/bd:/lists/Budget/items/" + fileId + "/workbook";
        var worksheetsEndpoint = workbookEndpoint + "/worksheets";
        var patchMethod = new HttpMethod("PATCH");
        var summaryTableRowJson = "{" +
                "'values': '" + val + ".csv'" +
            "}";
        var colNamePatchBody = new StringContent(summaryTableRowJson);
        colNamePatchBody.Headers.Clear();
        colNamePatchBody.Headers.Add("Content-Type", "application/json");
        var colNameRequestMessage = new HttpRequestMessage(patchMethod, worksheetsEndpoint +
            "('" + worksheetName + "')/range(address='Parameters!B2')")
        { Content = colNamePatchBody };
        var colNameResponseMessage = await client.SendAsync(colNameRequestMessage);
    }