Entity Reference to String

Hello,
I am new to CRM C# development. I have the following piece of code:
internal static Entity CreateContractLine(Prod productstar, decimal quantity, Guid userId, Guid contractId, IOrganizationService crmService, Guid parentContractLine, bool isRelated = false)
{

Entity crmdetail = new Entity(Constants.EntityName.ContractLine); //Constants is the name of a common file and it is referring to the logical name of an entity called ContractLine.

crmdetail[Constants.Attributes.ContractLine.ProductId] = new EntityReference(Constants.EntityName.Product, productstar.id); //left part is the schema name of an attribute called ProductId.



the ProductId attribute in the entity crmdetail is a single line of text field in CRM. I need to check if this attribute contains the word "Cheese Pizza" as part of its string. How do I do that?