DefaultQuerySqlGenerator.VisitPropertyParameter bug allows duplicate parameters

[MaxG117]

DefaultQuerySqlGenerator.VisitPropertyParameter attempts to avoid duplicates by comparing InvariantName with propertyParameterExpression.PropertyParameterName, but adds new parameters using propertyParameterExpression.Name for InvariantName:

            if (_relationalCommandBuilder.ParameterBuilder.Parameters
                .All(p => p.InvariantName != propertyParameterExpression.PropertyParameterName))
            {
                _relationalCommandBuilder.AddPropertyParameter(
                    propertyParameterExpression.Name,
            ...

You can reproduce by making a slight modification to the Where clause of the SimpleQueryTestBase.Where_poco_closure() test case:

            var customer = new Customer
            {
                CustomerID = "ALFKI",
            };

            await AssertQuery<Customer>(
                isAsync,
                cs => cs
                    .Where(c => c.Equals(customer) && c.Equals(customer))
                    .Select(c => c.CustomerID));

Even though the modification is pointless, it's valid syntax and it generates valid CommandText. But when executed against SqlServer EFCore provider, this test throws the following SqlException:

System.Data.SqlClient.SqlException : The variable name '@__customer_0_CustomerID' has already been declared. Variable names must be unique within a query batch or stored procedure.)

[MaxG117]

I think there's a bigger problem here in that the InvariantName is used as a Key to the parameterValues dictionary in RelationalCommand.CreateCommand, which uses the Name, not the PropertyParameterName. The LINQ to check for duplicates would have to look at the Name, but the Name is not part of the IRelationalParameter Interface.

[roji]

Note: moved this to the 3.0.0 milestone.