How I can check for null parameter in linq query for CRM

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Posted on by Prutal

I am using linq to query data from CRM, I want to check the conditions that have values and ignore the others , I used the following code:

return (from c in CTX.CreateQuery("trainingcourse")
    where CourseID == null || (Guid)c["trainingcourseid"] == CourseID
       && FromDate == null || (DateTime)c["startdate"] <= FromDate
       && ToDate == null || (DateTime)c["startdate"] >= ToDate
       && SearchText == null || ((string)c["title"]).Contains(SearchText) ||          
                                ((string)c["description"]).Contains(SearchText)
    select c)

But this cause the following application error

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

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KZee on at

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RE: How I can check for null parameter in linq query for CRM

LINQ is converted to FetchXml and there is no way in FetchXml to deal with your local variable on its own. You will get an error even if you try SearchText.Length > 0 or SearchText != "" or string.IsNullOrEmpty(SearchText).

Your code is good in terms of C# but not according to the engine converting your LINQ to FetchXml because of the way it works.

Following code works just fine because there it will not be converted to FetchXml.

var list = new List<string>();

(from s in list

where SearchText == null || s == SearchText

select s).Dump();

You can either create many if statements to first check your local variables for null to create different LINQ or the easiest would be to use QueryExpression which allows you to add conditions and you can add a condition if your variable is not null.

msdn.microsoft.com/.../gg334688.aspx
Prutal 10 on at

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RE: How I can check for null parameter in linq query for CRM

well yes the problem is because of the local variable, I want to check for the "trainingcourseid" only if "CourseID" is not null

in entity framework

i use something like this

CourseID is a parameter passed optionally

CTX.Table.Where(x=>CourseID ==null || x.CourseID==CourseID).ToList();

it suppose to work like an optional parameter for a method.

any suggestion how to achieve this.
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KZee on at

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RE: How I can check for null parameter in linq query for CRM

You are getting error message because are checking local variables for null in your LINQ query.

e.g. Following code works

(from c in serviceContext.CreateQuery("incident")

where ((string)c["title"]).Contains(SearchText) || ((string)c["description"]).Contains(SearchText)

select c

)

But if you introduce a null check for your local variable then you would get that error.

(from c in serviceContext.CreateQuery("incident")

where SearchText == null || ((string)c["title"]).Contains(SearchText) || ((string)c["description"]).Contains(SearchText)

select c

)

Following link explains how to use Contains in LINQ

msdn.microsoft.com/.../gg334415.aspx

I hope this helps.
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Daniel Wikell 2,360 on at

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RE: How I can check for null parameter in linq query for CRM

The error message you receive is because you are using .Contains which is not a supported feature in the Linq->fetchxml engine.

See this article for which LINQ-features are supported: msdn.microsoft.com/.../gg328328.aspx

If you want to use other LINQ-functions you will first have to convert the result to a regular list and then apply the contains criteria afterwards.

Also LINQ-fetchxml where-criterias are limited to the form of <property> <operator> <value> meaning that if you want to check if the trainingcourseid property is null you should check against that property on the left hand side and null on the right hand side. If you want to check if the local variable CourseID is null you should do it outside of the LINQ-query.

How I can check for null parameter in linq query for CRM

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