How to retrieve items using SPSiteDataQuery in SharePoint 2013

In this post we will see how to retrieve the items from multiple lists using SPSiteDataQuery in SharePoint 2013.

SPSiteDataQuery:
                It is used to retrieve data from list or from all list in the site collection (i.e. used for cross-site and cross-list queries).

SPSiteDataQuery.Webs:
                This property will be used to specify from where the data will be retrieved.

SPWeb.GetSiteData:
                It is used to retrieve the data.

Sample Code to retreive the Items from the Tasks list

string siteUrl = SPContext.Current.Web.Url;

string username=string.Empty;

using (SPSite site = new SPSite(siteUrl ))

{

   using (SPWeb web = site.RootWeb)

   {

      SPUser user = web.CurrentUser;

      username = user.LoginName;

      SPSiteDataQuery dataQuery = new SPSiteDataQuery();

    //if it is set to SiteCollection, the query considers all Web sites that are in the       same site collection as the current Web site. 

     dataQuery.Webs = "<Webs Scope=\"SiteCollection\">";

//if it set to Recursive the query considers only the current Web site and all       subsites of the current Web site. 

   //dataQuery.Webs = "<Webs Scope=\"Recursive\">";

   //107 Maps to the tasks list

     dataQuery.Lists = "<Lists ServerTemplate=\"107\" />";

     dataQuery.ViewFields = "<FieldRef Name=\"Title\" />" + "<FieldRef           Name=\"AssignedTo\" />" + "<FieldRef Name=\"DueDate\" />";

     string spQuery = "<Where><Eq><FieldRef Name=\"AssignedTo\"/><Value   Type='User'>" + username + "</Value></Eq></Where>";

     dataQuery.Query = spQuery;

     DataTable dt = web.GetSiteData(dataQuery);

     DataView dv = new DataView(dt);

     gvResult.DataSource = dv;

     gvResult.DataBind();

              

    }

}