Expression magic, how does it work? what gets evaluated at what time

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

  I am trying my luck here, I have a model which is like the following

  public class RowData : BaseBsonDefinition
  {
  .
    [BsonExtraElements]
    [BsonDictionaryOptions(DictionaryRepresentation.ArrayOfDocuments)]
    public Dictionary<string, object> Rows { get; set; } = new(StringComparer.OrdinalIgnoreCase);
  .
  }
  
  

  In result, the schema in the MongoDB looks like

  {
  "_id": {
      "$binary": {
        "base64": "HiuI1sgyT0OZmcgGUit2dw==",
        "subType": "03"
      }
    },
    "c1": "AAA",
    "c8": "Fully Vac",
    "c10": "",
  }
  

  Those c1, c8 and c10 fields are keys from the dictionary, my question is how to dynamic project those fields?

  I tried

  Builders<RowData>.Projection.Exclude(p => "c1")
  

  It seems the MongoDB driver can not handle a value directly.

  Anyone could point me in the correct direction?

  Thanks,
• 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)
  
• C# ef code first How to have a one-to-one relationship with

  How to make a one-to-one relationship with code first in c# desktop application, can you help
• LINQ select column that contains some array element

  I have a field "details" varchar(MAX) in my table with the detailed description of an item, I need to select the records that contain the keywords passed by the user in a string array.

  var searchTerms = new List<string> { "car", "black", "bike", "blue" };
  

  I tried to do it like this:

  var result = (from i in _contexto.itens
  where searchTerms.Any(d => i.details.Contains(d))
  select i.id);
  

  and I get the following error:

  The LINQ expression 'DbSet() .Where(i => __searchTerms_0 .Any(d => i.details.Contains(d)))' could not be translated. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or 'ToListAsync'. See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.

  I also tried this link's approach using the "SearchExtensions nuget package" and the same error occurs.

  How can I do this? or should I make a query for each item in the array?

  Example of a text I want to search for:

  It is a long established fact that a car will be distracted by the readable content of a page when looking at its bike. The point of using Lorem Ipsum is that it has a more-or-less normal distribution

  Thanks!
• How to use a database connection string in App.config?

  I use EF 6, and if I use a hardcode database connection in the OnConfiguring:

  protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
          {
              if (!optionsBuilder.IsConfigured)
              {
                  optionsBuilder.UseSqlServer("Data Source=.\\sqlexpress;Initial Catalog=MyOrders;Persist Security Info=True;User ID=sa;Password=***4n**user");
              }
          }
  

  the code will work well.

  but if I use a connect string in App.config:

  protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
      {
          if (!optionsBuilder.IsConfigured)
          {
              optionsBuilder.UseSqlServer(ConfigurationManager.AppSettings["DataBase"].ToString().Trim());                
          }
      }
  

  it will not work.

  the connect string in App.config:

      <add key="DataBase" value="Data Source=.\\sqlexpress;Initial Catalog=MyOrders;Persist Security Info=True;User ID=sa;Password=pk94newuser"/>
  

  the error message:

  Instance failure.
  

  the StrackTrace:

  at Microsoft.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo, SqlInternalConnectionTds connHandler, Boolean ignoreSniOpenTimeout, Int64 timerExpire, Boolean encrypt, Boolean trustServerCert, Boolean integratedSecurity, Boolean withFailover, SqlAuthenticationMethod authType)
     at Microsoft.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean ignoreSniOpenTimeout, TimeoutTimer timeout, Boolean withFailover)
     at Microsoft.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString connectionOptions, SqlCredential credential, TimeoutTimer timeout)
     at Microsoft.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(TimeoutTimer timeout, SqlConnectionString connectionOptions, SqlCredential credential, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance)
     at Microsoft.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, Boolean applyTransientFaultHandling, String accessToken, DbConnectionPool pool)
     at Microsoft.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)
     at Microsoft.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)
     at Microsoft.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
     at Microsoft.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
     at Microsoft.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
     at Microsoft.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
     at Microsoft.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
     at Microsoft.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
     at Microsoft.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
     at Microsoft.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry, SqlConnectionOverrides overrides)
     at Microsoft.Data.SqlClient.SqlConnection.Open(SqlConnectionOverrides overrides)
     at Microsoft.Data.SqlClient.SqlConnection.Open()
     at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerConnection.OpenDbConnection(Boolean errorsExpected)
     at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.OpenInternal(Boolean errorsExpected)
     at Microsoft.EntityFrameworkCore.Storage.RelationalConnection.Open(Boolean errorsExpected)
     at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteReader(RelationalCommandParameterObject parameterObject)
     at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.Enumerator.InitializeReader(Enumerator enumerator)
     at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.Enumerator.<>c.<MoveNext>b__19_0(DbContext _, Enumerator enumerator)
     at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerExecutionStrategy.Execute[TState,TResult](TState state, Func`3 operation, Func`3 verifySucceeded)
     at Microsoft.EntityFrameworkCore.Query.Internal.SingleQueryingEnumerable`1.Enumerator.MoveNext()
     at System.Linq.Enumerable.TryGetSingle[TSource](IEnumerable`1 source, Boolean& found)
     at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.Execute[TResult](Expression query)
     at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.Execute[TResult](Expression expression)
     at System.Linq.Queryable.FirstOrDefault[TSource](IQueryable`1 source)
  

  I want to know how to use a connect string in EF 6 correctly. Thanks!
• How to connect to MySQL server using Entity Framework Core

  I am using Visual Studio 2019 community edition. I want to connect to MySQL using Entity Framework core. I do not want to use Entity Framework 6.

  I am running into following issues:

  1. I created a new project using "ASP .NET CORE App and ASP .NET CORE Web App" template and it does not show option to add Entity Framework.

  

  2. If I use tools > Connect to Database option from menu, I do not see option to connect to MySQL. How can I enable this option.

  
• GetColumnName() in EF Core 6 returns property name not mapped column name

  I'm using EF Core 6 (6.0.2) with SQL Server 2019 with the following entity:

  public partial class MyEntity
  {
          [Column("External_ExternalId")]
          public Guid? ExternalId { get; set; }
  }
  

  I'm trying to get the mapped column name (External_ExternalId) for the ExternalId property with the following code:

  var entityType = dbContext.Model.FindEntityType(typeof(MyEntity));
  var property = entityType.GetProperties().Single(property => property.Name.Equals("ExternalId", StringComparison.OrdinalIgnoreCase));
  var columnName = property.GetColumnName(StoreObjectIdentifier.Create(property.DeclaringEntityType, StoreObjectType.Table).GetValueOrDefault());
  

  columnName is ExternalId instead of External_ExternalId. How can I get the actual name of the table's column? I tried GetColumnBaseName() but got the same result. Same if I configure the mapping with the fluent API.