Error while adding a user to site collection administrator

Question

 Hi All,

please help me from below issue.

 

get-access is button it reads input from text box , and it has to add that user id in to as a site collcetion administrator.

  

 

please see below code. where i am getting error.

 

private void button10_Click(object sender, EventArgs e)

{

string adduser = string.Empty;// textBox4.Text.Trim();

adduser = textBox4.Text.Trim();

if (Context == null)

{

Context = Get_Context();

}

Context.Load(Context.Site);

Context.Load(Context.Site.RootWeb);

Context.Load(Context.Site.RootWeb.SiteUsers);

Context.ExecuteQuery();

foreach (var scUser in Context.Site.RootWeb.SiteUsers)

{

if (scUser.IsSiteAdmin)

{

//here i am getting error 

User user = Web.EnsureUser(adduser);

// another formate tryed below also getting error same .

User user = Web.EnsureUser(@"domain\username").ToString(); 

 

Error : an Object referance is required for the non-static field, method, or property 'web.ensureUser(string)'

// Context.Site.RootWeb.SiteUsers.AddUser()

// Context.Site.RootWeb.SiteUsers.AddUser(scUser.Id);

//Context.Site.RootWeb.SiteUsers.AddUser(user);

Context.Site.RootWeb.SiteUsers.AddUser(user);

}

}

 

please can any one help me here.