The type or namespace name 'Office' could not be found

Question

Hi guys,

I am developing my first Outlook Add-In in C# and I am having the following problem.

Although the references are correctly added, the code is giving me the following error:

The type or namespace name 'Office' could not be found (are you missing a using directive or an assembly reference?)

I share with you the content of my ThisAddIn.cs file so you can see where the error occurs.

using Microsoft.Office.Core;
using Microsoft.Office.Interop.Outlook;
using System;
using System.IO;
using System.Runtime.InteropServices;
using Outlook = Microsoft.Office.Interop.Outlook;

namespace NewClientMatterIntake
{
    public partial class ThisAddIn
    {
        private Ribbon ribbon;

        private void ThisAddIn_Startup(object sender, EventArgs e)
        {
            ribbon = new Ribbon();
        }

        protected override Office.IRibbonExtensibility CreateRibbonExtensibilityObject()
        {
            return new Ribbon();
        }

        private void ThisAddIn_Shutdown(object sender, EventArgs e)
        {
            // Aquí puedes colocar código de limpieza si es necesario.
        }

        private string ReadTemplateFromFile(string templateName)
        {
            string filePath = Path.Combine(Environment.CurrentDirectory, "Templates", templateName);
            if (File.Exists(filePath))
            {
                try
                {
                    return File.ReadAllText(filePath);
                }
                catch (System.Exception ex) // Usamos System.Exception para evitar la ambigüedad
                {
                    System.Windows.Forms.MessageBox.Show($"Error reading template '{templateName}': {ex.Message}");
                }
            }
            else
            {
                System.Windows.Forms.MessageBox.Show($"Template file '{templateName}' not found.");
            }

            return string.Empty;
        }

        private void InternalButton_Click(Office.CommandBarButton Ctrl, ref bool CancelDefault)
        {
            string body = ReadTemplateFromFile("InternalTemplate.html");
            if (!string.IsNullOrEmpty(body))
            {
                CreateEmail("New Client/Matter Intake (Internal)", body);
            }
        }

        private void ExternalButton_Click(Office.CommandBarButton Ctrl, ref bool CancelDefault)
        {
            string body = ReadTemplateFromFile("ExternalTemplate.html");
            if (!string.IsNullOrEmpty(body))
            {
                CreateEmail("New Client/Matter Intake (External)", body);
            }
        }

        private void CreateEmail(string subject, string body)
        {
            var mail = Application.CreateItem(Outlook.OlItemType.olMailItem) as Outlook.MailItem;
            mail.Subject = subject;
            mail.BodyFormat = Outlook.OlBodyFormat.olFormatHTML;
            mail.HTMLBody = body + GetSignature();
            mail.Display();
        }

        private string GetSignature()
        {
            var tempMail = Application.CreateItem(Outlook.OlItemType.olMailItem) as Outlook.MailItem;
            string signature = tempMail.HTMLBody;
            Marshal.ReleaseComObject(tempMail);
            return signature;
        }

        #region VSTO generated code
        private void InternalStartup()
        {
            this.Startup += new EventHandler(ThisAddIn_Startup);
            this.Shutdown += new EventHandler(ThisAddIn_Shutdown);
        }
        #endregion
    }
}

I also share with you the references of my project.

Thank you in advance.

Answer 1

there is no Office.CommandBarButton, its full name is: Microsoft.Office.Core.CommandBarButton. as you have the namespace imported just use: "CommandBarButton"