SharePoint: How to remove all permissions of a user using CSOM?

Visual Studio > Project > References > Manage NuGet Packages > Online > Search 'Microsoft.SharePointOnline.CSOM' > Accept and Install

Visual Studio > Project > References > Manage NuGet Packages > Online > Search 'OfficeDevPnP.Core' > Accept and Install

private void btnRemove_Click(object sender, EventArgs e)

{

try

{

    progressBar1.Minimum = 0;

    progressBar1.Maximum = 100;

    progressBar1.Value = 1;

    ClientContext context = new ClientContext(txtSiteUrl.Text);

    context.RequestTimeout = 9999999;

    string decryptedPwd = txtAdminPassword.Text;

    foreach (char c in decryptedPwd)

    {

      securePassword.AppendChar(c);

    }

    
    if (rbtnOnpremise.Checked)

    {

      context.Credentials = new NetworkCredential(GetEnterpriseIDFromEmail(txtAdminID.Text),

      securePassword,

      txtDomain.Text);

    }

    else if (rbtnOnline.Checked)

    {

      context.Credentials = new SharePointOnlineCredentials(GetEnterpriseIDFromEmail(txtAdminID.Text) +       "@companyname.com",

      securePassword);

//Multifactor Authentication
//PnP.AuthenticationManager authManager = new PnP.AuthenticationManager();

//context = authManager.GetWebLoginClientContext(txtSiteUrl.Text);

    }

    Web web = context.Web;

    context.Load(web, w => w.Title, w => w.HasUniqueRoleAssignments);

    context.ExecuteQuery();

    string usr_loginName = "i:0#.w|" + txtDomain.Text + "\\" + GetEnterpriseIDFromEmail(txtResourceID.Text);

    User usr = web.EnsureUser(usr_loginName);

    context.Load(usr);

    progressBar1.Value = 5;

    //Remove User from Site

    if (web.HasUniqueRoleAssignments)

    {

  //!!!ExpensiveOperation!!!web.SiteUsers.RemoveByLoginName(usr_loginName);

  try

  {

      RoleAssignment directPermission = web.RoleAssignments.GetByPrincipal(usr);

      directPermission.DeleteObject();

      context.ExecuteQuery();

  }

  catch { }

 

    }

    progressBar1.Value = 10;

    //Remove User from Groups

    if (chkRemoveFromGroups.Checked)

    {

      GroupCollection userGroups = web.SiteGroups;

      context.Load(userGroups);

      context.ExecuteQuery();

  foreach (Group grp in userGroups)

  {

    try

    {

    grp.Users.Remove(usr);

    context.ExecuteQuery();

    }

    catch { }

  }

 

  }

  progressBar1.Value = 30;

    //Remove User from Lists

   if (chkRemoveFromList.Checked)

   {

      ListCollection lists = web.Lists;

      context.Load(lists, lsts => lsts.Where(l => l.HasUniqueRoleAssignments == true &&

                        l.Hidden == false &&

                        l.IsApplicationList == false &&

                        l.IsSiteAssetsLibrary == false).

                        Include(l => l.HasUniqueRoleAssignments, l => l.Title));

      context.ExecuteQuery();

  foreach (List list in lists)

  {

   if (list.HasUniqueRoleAssignments)

   {

     try

     {

       RoleAssignment listLevelPermission = list.RoleAssignments.GetByPrincipal(usr);

       listLevelPermission.DeleteObject();

       context.ExecuteQuery();

     }

     catch { }

   }

  }

 

 }

 progressBar1.Value = 50;

    //Remove User from Items

 if (chkRemoveFromItems.Checked)

 {

   ListCollection lists = web.Lists;

   context.Load(lists, lsts => lsts.Where(l => l.Hidden == false &&

                        l.IsApplicationList == false &&

                        l.IsSiteAssetsLibrary == false).

                        Include(l => l.Title));

   context.ExecuteQuery();

   foreach (List list in lists)

   {

     CamlQuery camlQuery = new CamlQuery();

     camlQuery.ViewXml = "<View Scope=\"RecursiveAll\"><RowLimit>10000</RowLimit></View>";

    ListItemCollection collListItem = list.GetItems(camlQuery);

    context.Load(collListItem,

    items => items.Where(

    item => item.HasUniqueRoleAssignments == true).

    Include(

    item => item.Id,

    item => item.DisplayName,

    item => item.HasUniqueRoleAssignments));

    context.ExecuteQuery();

    foreach (ListItem item in collListItem)

    {

    if (item.HasUniqueRoleAssignments)

    {

     try

     {

      RoleAssignment itemLevelPermission = item.RoleAssignments.GetByPrincipal(usr);

      itemLevelPermission.DeleteObject();

      context.ExecuteQuery();

     }

     catch { }

    }

 }

 }

 }

 progressBar1.Value = 100;

 MessageBox.Show("User Permissions removed!");

}

catch (Exception ex)

{

    MessageBox.Show("Error: " + ex.Message);

    progressBar1.Value = 100;

}

}