Want to create a windows application using C# to read and send mail using outlook

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C#

Outlook

I am able to send the mail using below code:

private void btn_Send_Click(object sender, EventArgs e)
       {
           try
           {
               Outlook._Application _app = new Outlook.Application();
               Outlook.MailItem mail = (Outlook.MailItem)_app.CreateItem(Outlook.OlItemType.olMailItem);
               mail.To = txt_To.Text;
               mail.Subject = txt_Subject.Text;
               mail.Body = txt_Message.Text;
               mail.Importance = Outlook.OlImportance.olImportanceNormal;
               ((Outlook._MailItem)mail).Send();
               MessageBox.Show("Your Message has been successfully sent.", "Message", MessageBoxButtons.OK, MessageBoxIcon.Information);
           }
           catch (Exception ex)
           {
               MessageBox.Show(ex.Message, "Message", MessageBoxButtons.OK, MessageBoxIcon.Error);
           }
       }

But i am facing an error while reading the mails from outlook, below is my code to read the mail:

private void btn_Receive_Click(object sender, EventArgs e)
       {
           try
           {
               Outlook._Application _app = new Outlook.Application();
               Outlook._NameSpace _ns = _app.GetNamespace("MAPI");
               Outlook.MAPIFolder inbox = _ns.GetDefaultFolder(Outlook.OlDefaultFolders.olFolderInbox);
               _ns.SendAndReceive(true);
               dt = new DataTable("Inbox");
               dt.Columns.Add("Subject", typeof(string));
               dt.Columns.Add("Sender", typeof(string));
               dt.Columns.Add("Body", typeof(string));
               dt.Columns.Add("Date", typeof(string));
               dataGrid.DataSource = dt;
               foreach (Outlook.MailItem item in inbox.Items)
               {
                   dt.Rows.Add(new object[] { item.Subject, item.SenderName, item.HTMLBody, item.SentOn.ToLongDateString() + "" + item.SentOn.ToLongDateString() });
               }

           }
           catch (Exception ex)
           {
               MessageBox.Show(ex.Message, "Message", MessageBoxButtons.OK, MessageBoxIcon.Error);
           }
       }

Error is: Unable to cast COM object of type 'System._ComObject' to interface type 'Microsoft.Office.Interop.Outlook.MailItem'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{00063034-0000-0000-C000-000000000046}' failed due to the following error: No such interface supported (Exception from HRESULT: 0*80004002 (E_NOINTERFACE)).

What I have tried:

After googling i found that we have to check If Item.Class=43, but when I try putting that If like: (if(item.Class=43)) condition, it shows a error stating 

Property or indexer '_MailItem.Class' cannot be assigned to -- it is read only 

Kindly help me to fix this.