How to use system.linq.dynamic to build dynamic where clause

See more:

ASP.NET

LINQ

C#3.5

lambda

Hey guys what's up?

We are now working on a project in my company (C # & ASP.Net) and in one of the pages, there is a mechanism which pulled some data from a table using WCF.

So far So good!

that data is stored inside a DTO class (let's name it Tikun94ActualPerformanceSummaryDTO) and eventually i converts it to an IEnumerable object like that:

IEnumerable<Tikun94ActualPerformanceSummaryDTO> filtered = this.Tikun94Summaries as IEnumerable<Tikun94ActualPerformanceSummaryDTO>;

(Tikun94Summaries is an object of type Tikun94ActualPerformanceSummaryDTO).

Now, These data are viewed through a table on the page and the user can filter the table using a few options that I give him.
While pressing the 'Submit' button, i want to iterate through the existing "filtered" (of type IEnumerable which I created before) and filter it by the values given me from the user.

For each value given from the user, I need to set a Where clause that filter "filtered" again and again. Now, because I do not want to query over and over again on the same IEnumerable "filtered" , I want to build the Where dynamically
and than run it only one time.

Lets see some code:

IEnumerable<Tikun94ActualPerformanceSummaryDTO> filtered = this.Tikun94Summaries as IEnumerable<Tikun94ActualPerformanceSummaryDTO>;
            IQueryable<Tikun94ActualPerformanceSummaryDTO> queryableData = filtered.AsQueryable();

Here (above), as you can see, i start by converting the IEnumerable object into IQueryable object in order to do the following:

string query = "filtered.Where(";

Now, i start checking the values given from the user and set the Where according to them using Switch Case (Let's take 2 cases as an example):

#region OperatorLineId

switch (cmbLine.SelectedValue)
            {
                case "0":
                    query += += "u => u.OperatorLineId == u.OperatorLineId  ";
                    break;
                default:
                    query += "u => u.OperatorLineId == Convert.ToInt32(cmbLine.SelectedValue) ";
                    break;
            }
#endregion

#region ExclusivityLine 
switch (ddlExclusivityLine.SelectedValue)
            {
                case "0":
                    query += "AND u => u.ExclusivityLine == u.ExclusivityLine ";
                    break;
                default:
                    query += "AND u => u.ExclusivityLine == ddlExclusivityLine.SelectedValue )";
                    break;
            }
            #endregion

var externals = new Dictionary<string, object>();
            externals.Add("filtered", queryableData);

And this is where i get the EXECPTION :-( :

var expression = System.Linq.Dynamic.DynamicExpression.Parse(typeof(IQueryable<Tikun94ActualPerformanceSummaryDTO>), query, new[] {externals});

Exception message:
"No property or field 'u' exists in type 'Tikun94ActualPerformanceSummaryDTO'"

I have a few guesses as to what I was doing wrong. Maybe i'm trying to use lambda expression where I'm not supposed to and maybe i'm not accessing the items inside the DTO cuurectly. Hoe can i access the values inside the DTO? maybe i'm not suppose to?

Eventually, i want to build that Where clause dynamically (in some of the switch cases i have to use operator '>' or '<').

I guess I have more than one error in writing this algorithm and I'd love to know what the correct syntax for writing this operation.

This is the Tikun94ActualPerformanceSummaryDTO class (There are of course many more parameters there, but here it's just for example):

using System;
using WcfSerialization = global::System.Runtime.Serialization;

namespace OpsReporting.DataContracts
{
    [WcfSerialization::DataContract(Namespace = "urn:OperatorsReporting.ServiceContracts", Name = "Tikun94ActualPerformanceParamDTO")]
	public partial class Tikun94ActualPerformanceSummaryDTO
    {
        public int operatorLineId;
        public string exclusivityLine;
        
        [WcfSerialization::DataMember(Name = "OperatorLineId", IsRequired = true, Order = 6)]
        public int OperatorLineId
        {
            get { return operatorLineId; }
            set { operatorLineId = value; }
        }

        [WcfSerialization::DataMember(Name = "ExclusivityLine", IsRequired = true, Order = 8)]
        public string ExclusivityLine
        {
            get { return exclusivityLine; }
            set { exclusivityLine = value; }
        }    
}

Thank you very much!

What I have tried:

Lots: see above