Where Clause In CAML Query

Question

I want to return all info for a specified user. The internal field name is UserAssigned. If I use this

foreach (ListItem listItem in listItemCollection)
{
  Console.WriteLine(listItem[“UserAssigned”]);
}

I get Microsoft.SharePoint.Client.FieldUserValue returned. How can I translate that to either set my CAML query to return everything for ID 31836 OR username Jones, Jack?

This is C# and CSOM

EDIT
This is the syntax I have...

string siteURL = "";
var ctx = new ClientContext(siteURL);
var web = ctx.Web;
List list = web.Lists.GetByTitle("ListTitle");
CamlQuery camlQuery = new CamlQuery();
camlQuery.ViewXml = "";

var listItemCollection = list.GetItems(camlQuery);

ctx.Load(listItemCollection,
         eachItem => eachItem.Include(
                     item => item,
                     item => item["ID"],
                     item => item["UserAssigned"]
                     ));

ctx.ExecuteQuery();

foreach (ListItem listItem in listItemCollection)
{
    Console.WriteLine(listItem["ID"];
    FieldUserValue un = (FieldUserValue)listItem["UserAssigned"];
    string unGood = un.LookupValue;
    Console.WriteLine(unGood);
}
Console.ReadLine();

Edit 2
I edited my syntax to be the below - but it is ignoring my where clause...

User user = ctx.Web.CurrentUser;
ctx.Load(user);
ctx.ExecuteQuery();
string itsme = user.Title;

CamlQuery camlQuery = new CamlQuery();
camlQuery.ViewXml = string.Format("<Where><Eq><FieldRef Name='UserAssigned' /><value Type='User'>{0}</Value></Eq></Where>", itsme);
var listItemCollection = list.GetItems(camlQuery);

ctx.Load(listItemCollection, 
         eachItem => eachItem.Include(
                 item => item,
                 item => item["ID"],
                 item => item["UserAssigned"]
                 ));

ctx.ExecuteQuery();

foreach (ListItem listItem in listItemCollection)
{
  Console.WriteLine(listItem["ID"];
  FieldUserValue un = (FieldUserValue)listItem["UserAssigned"];
  string unGood = un.LookupValue;
  Console.WriteLine(unGood);
}
Console.ReadLine();

Answer 1

To get the display name of the user from the listItem["UserAssigned"]

FieldUserValue user = (FieldUserValue)listItem["UserAssigned"];
string name = user.LookupValue; //display name

CAML query by this user

string query=string.Format("<View><Query><Where><Eq><FieldRef Name='UserAssigned'/><Value Type='User'>{0}</Value></Eq></Where></Query></View>", name );

Edit

to get the current logged in user

User user = ctx.Web.CurrentUser;    
ctx.Load(user);
ctx.ExecuteQuery();
string name = user.Title;

You can query one time using the current logged in user using the above CAML query

Answer 2

You do your query call before you pull the list items. Once you have your query then you get your list items based off of that.

Example below:

using (SPSite spSite = new SPSite(SPContext.Current.Web.Url))
{
    using (SPWeb spWeb = spSite.OpenWeb())
    {
        SPQuery query = new SPQuery();
        //Get your item by ID then pull what you want after.  This query returns a single list item from your ID
        query.ViewXml = string.Concat("<View><Query><Where><Eq><FieldName Name='ID' /><Value Type='Integer'>31836</Value></Eq></Where></Query><RowLimit>1</RowLimit></View>");

        string listUrl = spWeb.ServerRelativeUrl + "/Lists/YourList";
        SPList list = spWeb.GetList(listUrl);
        SPListItemCollection items = list.GetItems(query);

        foreach(SPListItem item in items) {
            //here is your stuff for that user (List Item)
        }
    }
}

I think this is what you are looking for. Hope this helps.