LINQ Count with condition - Count function

 var recordCount = ctx.Cases.Count(a => a.Role == "admin" && a.Userid="userid");

ref:- https://stackoverflow.com/questions/20755099/linq-count-with-condition

Linq Foreach and where caluse in asp.net

 var ProceedingsActiveList = CourtApplicationProceedingsList.Where(t => t.IsActive == true).ToList();

                ProceedingsActiveList.ForEach(p => { p.ConductingOfficerTypeName = ddlConductingProsecutor.Items.FindByValue(p.ConductingOfficerType.Value.ToString()).Text; p.LawOfficerName =  });

LINQ insert update delete - LINQ to SQL - ASP.NET C#

 https://www.c-sharpcorner.com/UploadFile/3d39b4/simple-select-insert-update-and-delete-using-linq-to-sql/

Advanced LINQ Query Techniques in C# with code samples

 https://efficientuser.com/2023/05/09/advanced-linq-query-techniques-in-c-with-code-samples/

OrderBy LINQ ASP.NET C#

 dtOpenVacancy.AsEnumerable().OrderByDescending(a => a.Field<int>("id"));

IF WANT TO USE WITH GRID DATABASE:-

dtOpenVacancy.AsEnumerable().OrderByDescending(a => a.Field<int>("id")).CopyToDataTable()

or

gridview

private void BindOpenVacancy()

        {

            DataTable dtOpenVacancy = Repository.GetAllOpenVacancy();

            if (dtOpenVacancy.Rows.Count > 0)

            {

                ViewState["vwOpenVacancy"] = dtOpenVacancy.AsEnumerable().OrderByDescending(a => a.Field<int>("id")).CopyToDataTable();

                grdOpenVacancy.DataSource = dtOpenVacancy.AsEnumerable().OrderByDescending(a => a.Field<int>("id")).CopyToDataTable(); 

            }

            grdOpenVacancy.DataBind();

        }

reference:- https://www.tutorialsteacher.com/linq/linq-sorting-operators-orderby-orderbydescending

Removing elements from var LINQ ASP.NET

 var exceptionList = 

                 allData.AsEnumerable().Where(a => dtOpenVacancy.AsEnumerable().Select(q => q.Field<string>("disciplinename")).Contains(a.Field<string>("discipline")) && dtOpenVacancy.AsEnumerable().Select(q => q.Field<string>("institutename")).Contains(a.Field<string>("institute")) && dtOpenVacancy.AsEnumerable().Select(q => q.Field<int>("cadreid")).Contains(int.Parse(ddlCadreType.SelectedItem.Value))).ToList();

                

                ViewState["dt2"]= allData.AsEnumerable().Except(exceptionList.AsEnumerable()).CopyToDataTable();

Use Tolist somewhere

or you can use removeall from List.

Compare List with string LINQ

DataTable dtOpenVacancy = ViewState["vwOpenVacancy"] as DataTable;

                var allData = dt3.AsEnumerable().Where(p => p.Field<string>("institute") != null);

 allData.Where(a => dtOpenVacancy.AsEnumerable().Select(q => q.Field<string>("disciplinename")).Contains( a.Field<string>("discipline")) && dtOpenVacancy.AsEnumerable().Select(q => q.Field<string>("institutename")).Contains(a.Field<string>("institute"))  && dtOpenVacancy.AsEnumerable().Select(q => q.Field<int>("cadreid")).Contains(int.Parse( ddlCadreType.SelectedItem.Value))).Count();

reference:- https://stackoverflow.com/questions/14257360/linq-select-objects-in-list-where-exists-in-a-b-c

LINQ get selected fields without Entity or modal

 var ssIPVac = allData.Where(s => s.Field<string>("institute") == ddlInstitute.SelectedItem.Text && s.Field<string>("discipline") == ddlDiscipline.SelectedItem.Text).Select(d => new { ss = d.Field<int>("ss"), ip = d.Field<int>("ip"), vacancy = d.Field<int>("vacancy") }).First();

                    txtSanctionedStrength.Text = ssIPVac.ss.ToString();

                    txtInPosition.Text = ssIPVac.ip.ToString();

                    txtVacancy.Text = ssIPVac.ip.ToString();

Remove records from LINQ ASP.NET C#

 var institutes = dt.AsEnumerable().Select(d => new { Institute = d.Field<String>("institute") }).Distinct();

            

            string json = js.Serialize(institutes.Where(a => a.Institute != null));

reference:- https://stackoverflow.com/questions/38381612/c-sharp-linq-remove-null-values-from-an-array-and-return-as-not-nullable

Group By with count LINQ ASP.NET C#

/var disciplineCount = dt.AsEnumerable().GroupBy(x => x.Field<string>("Discipline"), (key, g)=> new { discipline = key, disciplinecount = g.Count() }).ToList();

if((disciplineCount.Exists(d => d.discipline == DataBinder.Eval(e.Row.DataItem, "Discipline").ToString() && d.disciplinecount > 1)))

{

}

select and where query difference LINQ ASP.NET C# - with model or entity

 Select is mapping, we want to select two columns from five. (select columns) gives all rows

where will select all the columns but gives the rows with that values. (select rows) gives all columns

example:-

var employee = _db.EMPLOYEEs
    .Where(x => x.EMAIL == givenInfo || x.USER_NAME == givenInfo)
    .Select(x => new { x.EMAIL, x.ID });

reference:-https://stackoverflow.com/questions/6772267/linq-syntax-selecting-multiple-columns

 Where ~= Filter

select  = map the selected column


select for columns     and where for rows.

AND OR operator in Exists function LINQ - ASP.NET C# - without model or entity

var dt = GridView1.DataSource as DataTable;

                var a= dt.AsEnumerable().GroupBy(s => s.Field<string>("Discipline").ToString());

                

                

                //dt.DefaultView.Sort = sort;

                var final = dt.AsEnumerable().GroupBy(x => x.Field<string>("Discipline"), (key, g) => g.OrderByDescending(s => DateTime.ParseExact(s.Field<string>("PresentInstitutePostingDate") == ""?"01/01/1990": s.Field<string>("PresentInstitutePostingDate"), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture)).First()).Select(t=> new { PresentInstitutePostingDate = (DateTime.ParseExact(t.Field<string>("PresentInstitutePostingDate") == "" ? "01/01/1990" : t.Field<string>("PresentInstitutePostingDate"), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture)), Discipline= t.Field<string>("Discipline") });

                var tt = final.ToList();

  if (tt.Exists(o => o.PresentInstitutePostingDate == DateTime.ParseExact(DataBinder.Eval(e.Row.DataItem, "PresentInstitutePostingDate").ToString(), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture) && o.Discipline == DataBinder.Eval(e.Row.DataItem, "Discipline").ToString()))

                    {

                        e.Row.BackColor = System.Drawing.ColorTranslator.FromHtml("#0000ff");

                    }

Group By max date with empty values(date) LINQ Grid change color of row - ASP.NET C# - without model or entity

  var dt = GridView1.DataSource as DataTable;

                var a= dt.AsEnumerable().GroupBy(s => s.Field<string>("Discipline").ToString());

                

                

                //dt.DefaultView.Sort = sort;

                var final = dt.AsEnumerable().GroupBy(x => x.Field<string>("Discipline"), (key, g) => g.OrderByDescending(s => DateTime.ParseExact(s.Field<string>("PresentInstitutePostingDate") == ""?"01/01/1990": s.Field<string>("PresentInstitutePostingDate"), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture)).First()).Select(t=> new { PresentInstitutePostingDate = (DateTime.ParseExact(t.Field<string>("PresentInstitutePostingDate") == "" ? "01/01/1990" : t.Field<string>("PresentInstitutePostingDate"), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture)), Discipline= t.Field<string>("Discipline") });

                var tt = final.ToList();

                if (!string.IsNullOrEmpty(Convert.ToString(DataBinder.Eval(e.Row.DataItem, "PresentInstitutePostingDate"))))

                {

                    DateTime.ParseExact(DataBinder.Eval(e.Row.DataItem, "PresentInstitutePostingDate").ToString(), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture).Date.ToString("D");

                    if (tt.Exists(o => o.PresentInstitutePostingDate == DateTime.ParseExact(DataBinder.Eval(e.Row.DataItem, "PresentInstitutePostingDate").ToString(), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture) && o.Discipline == DataBinder.Eval(e.Row.DataItem, "Discipline").ToString()))

                    {

                        e.Row.BackColor = System.Drawing.ColorTranslator.FromHtml("#0000ff");

                    }

                }

Linq compare two columns with Exists in List - ASP.NET C# -without model or entity

 var dt = GridView1.DataSource as DataTable;

                var a= dt.AsEnumerable().GroupBy(s => s.Field<string>("Discipline").ToString());

                

                

                //dt.DefaultView.Sort = sort;

                var final = dt.AsEnumerable().GroupBy(x => x.Field<string>("Discipline"), (key, g) => g.OrderByDescending(s => DateTime.ParseExact(s.Field<string>("PresentInstitutePostingDate") == ""?"01/01/1990": s.Field<string>("PresentInstitutePostingDate"), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture)).First()).Select(t=> new { PresentInstitutePostingDate = (DateTime.ParseExact(t.Field<string>("PresentInstitutePostingDate") == "" ? "01/01/1990" : t.Field<string>("PresentInstitutePostingDate"), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture)), Discipline= t.Field<string>("Discipline") });

                var tt = final.ToList();

                if (!string.IsNullOrEmpty(Convert.ToString(DataBinder.Eval(e.Row.DataItem, "PresentInstitutePostingDate"))))

                {

                    DateTime.ParseExact(DataBinder.Eval(e.Row.DataItem, "PresentInstitutePostingDate").ToString(), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture).Date.ToString("D");

                    if (tt.Exists(o => o.PresentInstitutePostingDate == DateTime.ParseExact(DataBinder.Eval(e.Row.DataItem, "PresentInstitutePostingDate").ToString(), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture) && o.Discipline == DataBinder.Eval(e.Row.DataItem, "Discipline").ToString()))

                    {

                        e.Row.BackColor = System.Drawing.ColorTranslator.FromHtml("#0000ff");

                    }

                }

Linq select query ASP.NET C# - select two columns

 var dt = GridView1.DataSource as DataTable;

                var a= dt.AsEnumerable().GroupBy(s => s.Field<string>("Discipline").ToString());

                

                

                //dt.DefaultView.Sort = sort;

                var final = dt.AsEnumerable().GroupBy(x => x.Field<string>("Discipline"), (key, g) => g.OrderByDescending(s => DateTime.ParseExact(s.Field<string>("PresentInstitutePostingDate") == ""?"01/01/1990": s.Field<string>("PresentInstitutePostingDate"), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture)).First()).Select(t=> new { PresentInstitutePostingDate = (DateTime.ParseExact(t.Field<string>("PresentInstitutePostingDate") == "" ? "01/01/1990" : t.Field<string>("PresentInstitutePostingDate"), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture)), Discipline= t.Field<string>("Discipline") });

var tt = final.ToList();

if (!string.IsNullOrEmpty(Convert.ToString(DataBinder.Eval(e.Row.DataItem, "PresentInstitutePostingDate"))))

                {

                    DateTime.ParseExact(DataBinder.Eval(e.Row.DataItem, "PresentInstitutePostingDate").ToString(), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture).Date.ToString("D");

                    if (tt.Exists(o => o.PresentInstitutePostingDate == DateTime.ParseExact(DataBinder.Eval(e.Row.DataItem, "PresentInstitutePostingDate").ToString(), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture) && o.Discipline == DataBinder.Eval(e.Row.DataItem, "Discipline").ToString()))

                    {

                        e.Row.BackColor = System.Drawing.ColorTranslator.FromHtml("#0000ff");

                    }

                }

reference:- https://www.aspsnippets.com/Articles/SELECT-multiple-columns-from-DataTable-using-LINQ-in-C-and-VBNet.aspx

Group by with max date ASP.NET C# LINQ - without model or entity

  var dt = GridView1.DataSource as DataTable;

                var a= dt.AsEnumerable().GroupBy(s => s.Field<string>("Discipline").ToString());

                

                

                //dt.DefaultView.Sort = sort;

                var final = dt.AsEnumerable().GroupBy(x => x.Field<string>("Discipline"), (key, g) => g.OrderByDescending(s => DateTime.ParseExact(s.Field<string>("PresentInstitutePostingDate") == ""?"01/01/1990": s.Field<string>("PresentInstitutePostingDate"), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture)).First()).Select(t=> DateTime.ParseExact(t.Field<string>("PresentInstitutePostingDate") == "" ? "01/01/1990" : t.Field<string>("PresentInstitutePostingDate"), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture));

                var tt = final.ToList();

                if (!string.IsNullOrEmpty(Convert.ToString(DataBinder.Eval(e.Row.DataItem, "PresentInstitutePostingDate"))))

                {

                    if (tt.Exists(o => o == DateTime.ParseExact(DataBinder.Eval(e.Row.DataItem, "PresentInstitutePostingDate").ToString(), "mm/dd/yyyy", System.Globalization.CultureInfo.InvariantCulture)))

                    {

                        e.Row.BackColor = System.Drawing.ColorTranslator.FromHtml("#0000ff");

                    }

                }

Grouping with Max Linq ASP.NET C# - without model or entity

  var dt = GridView1.DataSource as DataTable;

                var a= dt.AsEnumerable().GroupBy(s => s.Field<string>("Discipline").ToString());

                

                

                //dt.DefaultView.Sort = sort;

                var final = dt.AsEnumerable().GroupBy(x => x.Field<string>("Discipline"), (key, g) => g.OrderByDescending(s => s.Field<Int64>("ID")).First()).Select(t=>t.Field<Int64>("ID"));

                var tt = final.ToList();

                

                if(tt.Exists(o=> o == Convert.ToInt64(DataBinder.Eval(e.Row.DataItem, "ID"))))

                        {

                    e.Row.BackColor = System.Drawing.ColorTranslator.FromHtml("#0000ff");

                }

reference:-https://stackoverflow.com/questions/35170408/linq-how-to-get-the-max-id-with-a-group-by-clause

Grouping with max in linq ASP.NET

 var ProcessAudList = ProcessAudService.Where(x => x.Active == "Y")

.GroupBy(x => x.ProjectSeq, (key,g)=>g.OrderByDescending(e=>e.ProjectValue).First());