Handle null entityreference in LINQ

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How to handle join when the EntityReference is null. For example

var info = (from cr in xrm.CreateQuery<new_course>()
join c in xrm.CreateQuery<Contact>()
on cr.course_contact.Id equals c.ContactId
where c.Id == courseGuid
select cr.title).FirstOrDefault();

when course_contact is null C# throws null exception

Microsoft.Crm.CrmArgumentNullException: attributeName ---> Microsoft.Crm.CrmArgumentNullException: attributeName ---> System.ArgumentNullException: Value cannot be null.
Parameter name: attributeName
--- End of inner exception stack trace ---
at Microsoft.Crm.Metadata.EntityMetadata.TryGetAttribute(String attributeName, NameMappingType mapping)
at Microsoft.Crm.Metadata.EntityMetadata.GetAttribute(String attributeName, NameMappingType mapping)
at Microsoft.Crm.Query.EntityExpression.FromSdkQueryVisitor.Visit(ConditionExpression condition)
at Microsoft.Crm.Query.EntityExpression.FromSdkQueryVisitor.Visit(FilterExpression filter)
at Microsoft.Crm.Query.EntityExpression.FromSdkQueryVisitor.Visit(QueryExpression query)
at Microsoft.Crm.Query.EntityExpression.InitializeFromQuery(QueryBase query)
at Microsoft.Crm.Query.EntityExpression.Converter.ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, Object value)
at Microsoft.Crm.BusinessEntities.ConversionHelpers.Convert(ICrmConversionContext conversionContext, Object source, Type destinationType)
at Microsoft.Crm.Extensibility.DictionaryMapper.Map(ParameterCollection inputs, ICrmConversionContext context)
at Microsoft.Crm.Extensibility.InternalOperationPlugin.Execute(IServiceProvider serviceProvider)
at Microsoft.Crm.Extensibility.V5PluginProxyStep.ExecuteInternal(PipelineExecutionContext context)
at Microsoft.Crm.Extensibility.VersionedPluginProxyStepBase.Execute(PipelineExecutionContext context)
--- End of inner exception stack trace ---
at Microsoft.Crm.Extensibility.VersionedPluginProxyStepBase.Execute(PipelineExecutionContext context)
at Microsoft.Crm.Extensibility.PipelineInstrumentationHelper.Execute(Boolean instrumentationEnabled, String stopwatchName, ExecuteWithInstrumentation action, PipelineExecutionContext context)
at Microsoft.Crm.Extensibility.Pipeline.<>c__DisplayClass2_1.<Execute>b__0()

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RaviKashyap 55,410 Moderator on at

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Hi,

Try with this-

===========

var info = (from cr in xrm.CreateQuery<new_course>()

join c in xrm.CreateQuery<Contact>()

on cr.course_contact != null

&& cr.course_contact.Id equals c.ContactId

where c.Id == courseGuid

select cr.title).FirstOrDefault();

==============

Hope this helps.

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Community Member on at

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Hi Ravi,

We cannot use multi-condition join using && however, I have tried using left join to check course_contact is not null as below

var info = (from cor in xrm.CreateQuery<new_course>()

join con in xrm.CreateQuery<Contact>()

on new { a = cor.course_contact != null, contactId = cor.course_contact.Id }

equals new { a = true, contactId = con.Id } into courseContact

from cc in courseContact.DefaultIfEmpty()

select cor.title

).FirstOrDefault();

but I am getting the error below

Invalid 'join' condition. An entity member is invoking an invalid property or method.

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RaviKashyap 55,410 Moderator on at

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Sorry, I didn't have any project to cross check however I tried the SDK sample and tried the similar query. You can put the null check in where clause.

Try this

================

var info = (from cr in xrm.CreateQuery<new_course>()

join c in xrm.CreateQuery<Contact>()

on cr.course_contact.Id equals c.ContactId

where cr.course_contact != null

&& c.Id == courseGuid

=============================

Hope this helps.

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Community Member on at

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Tried already. Didn't work :(

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Sid07 285 on at

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I have seen this error before. u can try below change and update me if it worked or not

var info = (from cr in xrm.CreateQuery<new_course>()

join c in xrm.CreateQuery<Contact>()

on cr.GetAttributeValue<EntityReference>("course_contact").Id equals c.GetAttributeValue<EntityReference>("contactid").Id

where c.GetAttributeValue<Guid>("contactid").Id == courseGuid

select cr.title).FirstOrDefault();

Also please check if course_contact is right name of the field ?

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Community Member on at

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Hi Siddesh

It's the same error as mentioned in my first post i.e. Microsoft.Crm.CrmArgumentNullException: attributeName...

I think query result or exception should be the same whether we will use early or late bound.

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Yagasoft 240 on at

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Think of the query in terms of FetchXML; so compare directly with the lookup itself:

var info = (from cr in xrm.CreateQuery<new_course>()

join c in xrm.CreateQuery<Contact>()

on cr.course_contact equals c.ContactId

where c.Id == courseGuid

select cr.title).FirstOrDefault();

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Bipin D365 28,983 Moderator on at

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Hi,

Can you try below code.

I have changed the order - on c.ContactId equals cr.course_contact.Id

var info = (from cr in xrm.CreateQuery<new_course>()

join c in xrm.CreateQuery<Contact>()

on c.ContactId equals cr.course_contact.Id

where c.Id == courseGuid

select cr.title).FirstOrDefault();

See below link for more complex linq queries.

https://github.com/microsoft/PowerApps-Samples/blob/master/cds/orgsvc/C%23/QueriesUsingLINQ/ComplexQueries/SampleProgram.cs

If found helpful, Please mark my answer verified.

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