Dynamic Linq query on relationship with foreign key of type Guid
c# dynamic-linq expression-trees sql
Question
I'm using System.Linq.Dynamic to query an IQueryable datasource dynamically using a where-clause in a string format, like this:
var result = source.Entities.Where("City = @0", new object[] { "London" });
The example above works fine. But now I want to query on a foreign key-property of type Guid like this:
var result = source.Entities.Where("CompanyId = @0", new object[] { "838AD581-CEAB-4B44-850F-D05AB3D791AB" });
This won't work because a Guid can't be compared to a string by default. And I have to provide the guid as a string because it's originally coming from a json-request and json does not support guid's.
Firstly, is this even a correct way of querying over a relationship or is there an other syntax for doing this?
Secondly, how do I modify Dynamic.cs from the Dynamic Linq-project to automatically convert a string to guid if the entity-property being compared with is of type guid?
Accepted Answer
You have many ways for solving. Simplest, as i think, will be change your query like this
var result = source.Entities.Where("CompanyId.Equals(@0)", new object[] { Guid.Parse("838AD581-CEAB-4B44-850F-D05AB3D791AB") });
If you want use operators = and == then in Dynamic.cs you need change interface IEqualitySignatures : IRelationalSignatures like this
interface IEqualitySignatures : IRelationalSignatures
{
....
F(Guid x, Guid y);
....
}
after that you can use next query
var result = source.Entities.Where("CompanyId=@0", new object[] { Guid.Parse("838AD581-CEAB-4B44-850F-D05AB3D791AB") });
OR
var result = source.Entities.Where("CompanyId==@0", new object[] { Guid.Parse("838AD581-CEAB-4B44-850F-D05AB3D791AB") });
But if you want use string parameter you need change ParseComparison method in ExpressionParser class. You need add yet another checking for operand types like this
....
//you need add this condition
else if(left.Type==typeof(Guid) && right.Type==typeof(string)){
right = Expression.Call(typeof(Guid).GetMethod("Parse"), right);
}
//end condition
else {
CheckAndPromoteOperands(isEquality ? typeof(IEqualitySignatures) : typeof(IRelationalSignatures), op.text, ref left, ref right, op.pos);
}
....
and then you query will be work
var result = source.Entities.Where("CompanyId = @0", new object[] { "838AD581-CEAB-4B44-850F-D05AB3D791AB" });
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