How to projection fields for a dictionary (C#, MongdoDB)

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• C# - Adding condition to func results in stack overflow exception

  I have a func as part of specification class which sorts the given iqueryable

  Func<IQueryable<T>, IOrderedQueryable<T>>? Sort { get; set; }
  

  When i add more than one condition to the func like below , it results in stack overflow exception.

  spec.OrderBy(sc => sc.Case.EndTime).OrderBy(sc => sc.Case.StartTime);
  

  The OrderBy method is implemented like this

  public ISpecification<T> OrderBy<TProperty>(Expression<Func<T, TProperty>> property)
      {
          _ = Sort == null ? Sort = items => items.OrderBy(property) : Sort = items => Sort(items).ThenBy(property);
          return this;
      }
  

  Chaining or using separate lines doesn't make a difference.

  This problem gets resolved if I assign a new instance of the specification and set it's func, but i don't want to be assigning to a new instance everytime. Please suggest what am i missing here and how to reuse the same instance (if possible).
• How do I add new DataSource to an already Databinded CheckBoxList

  i'm building a web form that show Database's item(Tables, Rows, FK,...)

  I have a CheckBoxList of Tables (chkListTable) which will show a new CheckBoxList of Rows (chkListRow) everytime I SelectedIndexChanged from chkListTable. The problem is i can show the items from chkListTable with 1 selected item. But i don't know how to show chkListRow if multiple item from chkListTable are selected.

  Here are my codes:

  aspx:

  <div>
               <asp:Label ID="Label2" runat="server" Text="Table: "></asp:Label>
               <asp:CheckBoxList ID="chkListTable" runat="server"
                   DataTextField="name"
                   DataValueFeild="name"
                   AutoPostBack="true"
                   OnSelectedIndexChanged="chkListTable_SelectedIndexChanged">
               </asp:CheckBoxList>
          </div>
          <div>
               <asp:CheckBoxList ID="chkListRow" runat="server"
               DataTextField="COLUMN_NAME"
               DataValueField="COLUMN_NAME"
               RepeatDirection="Horizontal">
               </asp:CheckBoxList>
          </div>
  

  aspx.cs:

  protected void chkListTable_SelectedIndexChanged(object sender, EventArgs e)
      {
          tableName.Clear();
          
          foreach (ListItem item in chkListTable.Items)
          {
              if(item.Selected)
              {
                  tableName.Add(item.Text.Trim());
              }    
          }
  
          for(int i = 0; i < tableName.Count; i++)
          {
              String query = "USE " + dbname +
                  " SELECT * FROM information_schema.columns" +
                  " WHERE table_name = '" + tableName[i] + "'" +
                  " AND COLUMN_NAME != 'rowguid'";
              chkListRow.DataSource = Program.ExecSqlDataReader(query);
              chkListRow.DataBind(); 
              Program.conn.Close();
          }
      }
  

  Program.cs:

  public static bool Connect()
      {
          if (Program.conn != null && Program.conn.State == ConnectionState.Open)
              Program.conn.Close();
          try
          {
              Program.conn.ConnectionString = Program.constr;
  
              Program.conn.Open();
  
              return true;
          }
  
          catch (Exception e)
          {
              return false;
          }
      }
  
      public static SqlDataReader ExecSqlDataReader(String query)
      {
          SqlDataReader myreader;
          SqlCommand sqlcmd = new SqlCommand(query, Program.conn);
          sqlcmd.CommandType = CommandType.Text;
          if (Program.conn.State == ConnectionState.Closed) Program.conn.Open();
          try
          {
              myreader = sqlcmd.ExecuteReader();
              return myreader;
              myreader.Close();
          }
          catch (SqlException ex)
          {
              Program.conn.Close();
              return null;
          }
      }
  

  I want my display to be like this:

  [x]Table1 [x]Table2 [ ]Table3
  [ ]Row1(Table1) [ ]Row2(Table1) [ ]Row3(Table1)
  [ ]Row1(Table2) [ ]Row2(Table2)
  
• Error message : MongoServerError: bad auth :Authentication failed

  What is the reason behind this error? this code I am using to connect to DB.

  const uri =`mongodb+srv://${process.env.DB_USER}:${process.env.DB_PASSWORD}@cluster0.xft2s.mongodb.net/myFirstDatabase?retryWrites=true&w=majority`;
  
• In Mongo, If a document I'm saving "Prateek" then I don't want on the next create operation even the "prateek" or "praTEEK", etc is saved

  //** If I'm adding a new document with the name: "India", then I don't want that the DB allow another name with the name: "INDIA", "india", "indIA", etc. I'm new and learning, help would be great!!**

  // Controller

  var Dinosaur = require('../models/dinosaurs');
  
  //addDino
  module.exports.addDino = (req, res) => {
      var name = req.body.name;
      var type = req.body.type;
      var height = req.body.height;
      var weight = req.body.weight;
      var Period = req.body.Period;
  
      req.checkBody('name', 'Name is required').notEmpty();
  
      var errors = req.validationErrors();
      if (errors)
          return res.status(400).send({
              message: 'Name is Required'
          });
      else {
          let newDino = {
              name: name,
              type: type,
              height: height,
              weight: weight,
              Period: Period
          }
          Dinosaur.addDino(newDino, (err, result) => {
              if (err) {
                  if (err.name) return res.status(409).send({
                      message: name + ' Already Exist'
                  });
                  else if (err.url) return res.json({ status: false, error: { url: "Url already exist" }, message: err.url });
                  else return res.json(err, "Server Error");
              }
              else {
                  return res.status(200).send({
                      message: "Done"
                  });
              }
          });
      }
  }
  

  // Model

  var mongoose = require('mongoose');
  
  //dinosaur schema
  var DinosaurSchema = mongoose.Schema({
      name: {
          type: String,
          unique: true
      },
      type: {
          type: String
      },
      height: {
          type: Number
      },
      weight: {
          type: Number
      },
      Period: {
          type: String
      }
  });
  
  var Dinosaur = mongoose.model('dinosaur', DinosaurSchema);
  
  //add
  module.exports.addDino = (query, callback) => {
      Dinosaur.create(query, callback);
  }
  

  // GetAll, Already Created a new document with the name "Brachiosaurus"

  

  // > Create, a new create with the first letter lower case "brachiosaurus", Don't want it to be pushed.

  //Get All, Got pushed.
• How update a specific value on mongodb database using CRUD operation?

  I have to change a specific value of a field in MongoDB. I have tried using put method using CRUD operation but could not figure it. can you help me by giving proper code snippet?
• How to send query with variables from Rstudio to Mongo database?

  I'm trying to send query to my Mongo database depending on a variable producted in my R code. Unfortunately, Mongo query needs double quotes and the function "paste" in R doesn't support it. Here my variable is equal to "test01" but it will change at each iteration. I tried to build a great character chain named "req" thanks to some "paste" functions with returns:

  req
  > "'{\"id\":\"test01\"}'"
  cat(req)
  > '{"id":"test01"}'

  Which seems to be as a query but when I try :

  connection_db$count(jsonlite::toJSON(req))

  It returns [0] whereas if if try :

  connection_db$count('{"id":"test01"}')

  It returns [1]. Can you help me please?