CODEWITHSUNDEEP
linqentity-framework
birdus
birdus

Reputation: 7504

Building dynamic where clauses in LINQ to EF queries

I'm trying to build a where clause dynamically in a LINQ query which references tables via EF, but I'm getting the following error:

'ClaimantLastName' could not be resolved in the current scope or context. Make sure that all referenced variables are in scope, that required schemas are loaded, and that namespaces are referenced correctly. Near member access expression, line 6, column 2.

Here is what I'm trying:

string whereClause = string.Format("ClaimantLastName = '{0}' and ClaimantSSN = '{1}'", lastName, ssn);

I've also tried it without the single quotes to no avail.

Here is the actual query:

return db.Claims.Where(whereClause).Select(
                    u => new AdvancedSearchResult
                    {
                        ClaimNumber = u.ClaimNumber,
.
.
.

Is what I'm trying to do possible? It seems really basic. Where am I going wrong?

UPDATE: Here is the Claim entity.

public static Claim CreateClaim(global::System.Int32 id, global::System.String claimantFirstName, global::System.String claimantLastName, global::System.String claimantSSN, global::System.DateTime dateOfInjury, global::System.String claimNumber, global::System.String claimantMiddleName, global::System.String claimantAddress1, global::System.String claimantAddress2, global::System.String claimantCity, global::System.String claimantState, global::System.String claimantZip, global::System.DateTime claimantDateOfBirth, global::System.String compensability, global::System.Boolean injuryType, global::System.String jurisdictionState, global::System.String status, global::System.String condition, global::System.String managingBranch, global::System.String bodyPart, global::System.String acceptedBodyPart, global::System.Boolean pGCase, global::System.String employersDefenseAttorney, global::System.String accidentDescription, global::System.String claimExaminerFirstName, global::System.String claimExaminerLastName, global::System.String claimExaminerEmail, global::System.String claimantAttorney, global::System.String workerId, global::System.String workerType)
{
    Claim claim = new Claim();
    claim.Id = id;
    claim.ClaimantFirstName = claimantFirstName;
    claim.ClaimantLastName = claimantLastName;
    claim.ClaimantSSN = claimantSSN;
    claim.DateOfInjury = dateOfInjury;
    claim.ClaimNumber = claimNumber;
    claim.ClaimantMiddleName = claimantMiddleName;
    claim.ClaimantAddress1 = claimantAddress1;
    claim.ClaimantAddress2 = claimantAddress2;
    claim.ClaimantCity = claimantCity;
    claim.ClaimantState = claimantState;
    claim.ClaimantZip = claimantZip;
    claim.ClaimantDateOfBirth = claimantDateOfBirth;
    claim.Compensability = compensability;
    claim.InjuryType = injuryType;
    claim.JurisdictionState = jurisdictionState;
    claim.Status = status;
    claim.Condition = condition;
    claim.ManagingBranch = managingBranch;
    claim.BodyPart = bodyPart;
    claim.AcceptedBodyPart = acceptedBodyPart;
    claim.PGCase = pGCase;
    claim.EmployersDefenseAttorney = employersDefenseAttorney;
    claim.AccidentDescription = accidentDescription;
    claim.ClaimExaminerFirstName = claimExaminerFirstName;
    claim.ClaimExaminerLastName = claimExaminerLastName;
    claim.ClaimExaminerEmail = claimExaminerEmail;
    claim.ClaimantAttorney = claimantAttorney;
    claim.WorkerId = workerId;
    claim.WorkerType = workerType;
    return claim;
}

UPDATE: Added Paul's suggested code as a trial. This actually works.

whereClause = string.Format("ClaimantLastName = \"{0}\" and ClaimantSSN = \"{1}\"", lastName, ssn);

                   List<URIntake.Claim> claims = new List<Claim>();
URIntake.Claim claim = new Claim();
claim.ClaimantFirstName = "Jay";
claim.ClaimantLastName = "Williams";
claim.ClaimantSSN = "654219870";
claim.ClaimantDateOfBirth = new DateTime(1993, 1, 2);
claims.Add(claim);

claim = new Claim();
claim.ClaimantFirstName = "Santa";
claim.ClaimantLastName = "Claus";
claim.ClaimantSSN = "012345678";
claim.ClaimantDateOfBirth = new DateTime(1893, 1, 2);
claims.Add(claim);

List<AdvancedSearchResult> selectedClaims = claims.AsQueryable().Where(whereClause).Select(
    u => new AdvancedSearchResult
    {
        ClaimNumber = u.ClaimNumber,
        DateOfBirth = u.ClaimantDateOfBirth,
        DateOfInjury = u.DateOfInjury,
        Denied = u.Compensability == "Denied"
    }).ToList();

Upvotes: 2

Views: 32087

Answers (5)

user1914530
user1914530

Reputation:

Here's an example using System.Linq.Expressions. Although the example here is specific to your Claim class you can make functions like this generic and then use them to build predicates dynamically for all your entities. I've been using recently to provide users with a flexible search for entities on any entity property (or groups of properties) function without having to hard code all the queries.

public Expression<Func<Claim, Boolean>> GetClaimWherePredicate(
    String name, 
    String ssn)
{
  //the 'IN' parameter for expression ie claim=> condition
  ParameterExpression pe = Expression.Parameter(typeof(Claim), "Claim");

  //Expression for accessing last name property
  Expression eLastName = Expression.Property(pe, "ClaimantLastName");

  //Expression for accessing ssn property
  Expression eSsn = Expression.Property(pe, "ClaimantSSN");

  //the name constant to match 
  Expression cName = Expression.Constant(name);

  //the ssn constant to match 
  Expression cSsn = Expression.Constant(ssn);

  //the first expression: ClaimantLastName = ?
  Expression e1 = Expression.Equal(eLastName, cName);

  //the second expression:  ClaimantSSN = ?
  Expression e2 = Expression.Equal(eSsn, cSsn);

  //combine them with and
  Expression combined = Expression.And(e1, e2);

  //create and return the predicate
  return Expression.Lambda<Func<Claim, Boolean>>(
    combined, 
    new ParameterExpression[] { pe });
}

Upvotes: 8

Khalil10
Khalil10

Reputation: 69

the simple way is to use LINQExtension with LINQKIT 

using (var context = new workEntities() )
{

    Dictionary<string, List<string>> dictionary = new Dictionary<string, List<string>>();
    dictionary["Title"] = new List<string> {  
                    "Network Engineer", 
                    "Security Specialist", 
                    "=Web Developer"
                };
    dictionary["Salary"] = new List<string> { ">=2000" };
    dictionary["VacationHours"] = new List<string> { ">21" };
    dictionary["SickLeaveHours"] = new List<string> { "<5" };                
    dictionary["HireDate"] = new List<string> { 
                    ">=01/01/2000",
                    "28/02/2014" 
                };
    dictionary["ModifiedDate"] = new List<string> { DateTime.Now.ToString() };

    var data = context.Employee.CollectionToQuery(dictionary).ToList();
}

Upvotes: 1

Eng-Mohamed Abdulwahab
Eng-Mohamed Abdulwahab

Reputation: 51

    public class SearchField
    {
        public string Name { get; set; }
        public string @Value { get; set; }
        //public string Operator { get; set; }

        public SearchField(string Name, string @Value)
        {
            this.Name = Name;
            this.@Value = @Value;
            //Operator = "=";
        }
    }

    public class FilterLinq<T>
    {
        public static Expression<Func<T, Boolean>> GetWherePredicate(params SearchField[] SearchFieldList)
        {

            //the 'IN' parameter for expression ie T=> condition
            ParameterExpression pe = Expression.Parameter(typeof(T), typeof(T).Name);

            //combine them with and 1=1 Like no expression
            Expression combined = null;

            if (SearchFieldList != null)
            {
                foreach (var fieldItem in SearchFieldList)
                {
                    //Expression for accessing Fields name property
                    Expression columnNameProperty = Expression.Property(pe, fieldItem.Name);


                    //the name constant to match 
                    Expression columnValue = Expression.Constant(fieldItem.Value);

                    //the first expression: PatientantLastName = ?
                    Expression e1 = Expression.Equal(columnNameProperty, columnValue);

                    if (combined == null)
                    {
                        combined = e1;
                    }
                    else
                    {
                        combined = Expression.And(combined, e1);
                    }
                }
            }

            //create and return the predicate
            return Expression.Lambda<Func<T, Boolean>>(combined, new ParameterExpression[] { pe });
        }

    }

And You Can call it for any Class

ClinicEntities x = new ClinicEntities();

  dataGridView1.DataSource = x.Patient
                          .Where(
FilterLinq<Patient>.GetWherePredicate(
new SearchField("PatientNameEnglish", "Mona Mohamed Ali"), 
new SearchField("PatientHusbandName", "Ahmed Sallam Kareem"))).ToList();

Finally Thanks for bmused

Upvotes: 1

Charles380
Charles380

Reputation: 1279

I personally really like to use PredicateBuilder because it still has the LINQ look and feel, and not some magic string. You can have all sorts of conditions then add the clause to there predicate and it will compile all nice and clean for you.

http://www.albahari.com/nutshell/predicatebuilder.aspx

Here is a cut up sample from my own code:

var predicate = PredicateBuilder.True<MarketingCabinetItem>();

//add vendor filter
if (vendorComboBox.SelectedValue != null && !String.IsNullOrEmpty(vendorComboBox.SelectedValue.ToString()))
{
    var vend = vendorComboBox.SelectedValue.ToString();
    predicate = predicate.And(m => m.Vendor == vend);
    vendPredicate.And(v => v.VendorName == vend);
}


//get all mkt item types in category
if (categoryComboBox.SelectedValue != null)
{
    var mktCatId = Guid.Parse(categoryComboBox.SelectedValue.ToString());
    predicate = predicate.And(p => p.CategoryCategoryId == mktCatId);
}

// get the marketing items using the inner and outer
var mktItems = (from mi in ctx.MarketingItem.AsExpandable()
                join mType in ctx.ItemType.AsExpandable() on mi.MarketingItemTypeId equals mType.Id
                join mktCat in ctx.Category.AsExpandable() on mType.MarketingItemCategoryId equals mktCat.Id
                join att in ctx.Attachment.AsExpandable() on mi.Id equals att.MarketingItemId
                join pri in ctx.Priority.AsExpandable() on mi.PriorityId equals pri.Id


                select new MarketingCabinetItem
                {
                   Id = mi.Id,
                   Title = mi.Title,
                   ItemTypeDescription = mType.Description,
                   PriorityLevel = pri.Level,
                   StartDate = mi.StartDate,
                   ExpirationDate = mi.ExpirationDate,
                   HasAttachments = att != null,
                   CategoryDescription = mktCat.Description
               }).Where(predicate).ToList();

Upvotes: 6

Paul Sullivan
Paul Sullivan

Reputation: 2875

You could/need to use dynamic linq

http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx

db.Where("Something = @0 And SomethingElse = @1", "Blah", 42)

Seems to be how it is handled (note the lack of need for string.Format)

Upvotes: 4

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