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The ToListAsync throws value cannot be null. ' an exception

Having IQueryable 

var query = _db
    .ApplicationPaidServices
    .Include(it => it.Application)
    .Include(it => it.Application.User)
    .Where(it => Enum1.Value1 == it.Application.Enum1)
    .Skip(0);

Execution 1

 var result1 = await (from it in query
                      select it)
            .ToListAsync();

work.

Execution 2

 var result2 = await (from it in query
                      select
                      new
                      { it })
                     .ToListAsync();

Issues ArgumentNullException

with the message: The value cannot be null. Parameter name: arguments [2]

stack trace

System.Dynamic.Utils.ContractUtils.RequiresNotNull (object value, string paramName, int index) System.Dynamic.Utils.ExpressionUtils.RequiresCanRead (expression expression, string paramName, int idx) System.Dynamic.Utils.ExpressionUtils.ValidateOneArgument (MethodBase , ExpressionType nodeKind, Expression Arguments, ParameterInfo pi, String MethodParamName, String ArgumentParamName, Int index) System.Dynamic.Utils.ExpressionUtils.ValidateArgumentTypes (MethodBase Method, ExpressionType nodeKind, Expressions.ReadOnlyCollection SystemLaram Arguments, String Method Call (Expression instance, MethodInfo method, IEnumerable args) Microsoft.EntityFrameworkCore.Query.ExpressionVisitors.Internal.IncludeExpressionVisitor.VisitMethodCall (MethodCallExpressionCallExpression method) System.Linq.Expressions.MethodCallExpression.Accept (ExpressionVisitor Visitor)

By commenting either Where

or Skip

on the initial request, fixes the error.

I don't know what the reason is.

Using Npgsql.EntityFrameworkCore.PostgreSQL

and.NET Core 1.1

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1 answer


Tired of this today. One possible solution is to wait ToListAsync

until Select()

:



        var paged = await queryable
            .OrderBy(m => m.Name)
            .Skip(0).Take(30)
            .ToListAsync();

        var result = paged.Select(ViewModel.Map).ToList();
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