Error: LINQ to Entities does not recognize the method 'System.String ToString(System.Object)' method occurs while string conversion

c# entity-framework-6 linq

Question

I have an entity framework's EDMX generated class.

public partial class Contact : EntityBase
{
    public Contact()
    {
    }

    public string FirstName { get; set; }
    public string MiddleName { get; set; }
    public string LastName { get; set; }
    public string NickName { get; set; }
    public Nullable<System.DateTime> DOB { get; set; }
}

I've a LINQ expression for searching a text against all above properties.

Expression<Func<Contact, bool>> cntExpression = p => p.LastName.ToLower().Trim().Contains(searchedText) ||
                p.FirstName.ToLower().Trim().Contains(searchedText) ||
                p.MiddleName.ToLower().Trim().Contains(searchedText) ||
                p.NickName.ToLower().Trim().Contains(searchedText) ||
                (p.DOB.HasValue && p.DOB.Value.ToShortDateString().ToLower().Trim().Contains(searchedText));

'searchedText' is a variable containing the text value which has to be matched.

I now used business logic class's method to filter records using the above LINQ expression.

IQueryable<Contact> qryContact = _cntMgr.GetFiltered(cntExpression);

Till here the code gets executed, but it throws error while looping through Contact records existing in the above IQueryable result.

foreach (var contact in qryContact)
            {
                if (contact!=null)
                {
                    // Some code executes here..
                }
            }

The error I get is this:

 LINQ to Entities does not recognize the method 'System.String ToString(System.Object)' method, and this method cannot be translated into a store expression.

I already know that System.String ToString is not supported in Linq to Entities, but I need a solution or a workaround for this issue.

Please help me in getting it fixed.

Thanks in advance.

1
1
9/1/2015 11:28:31 AM

Accepted Answer

Your problem is related to the ToShortDateString call you have. One way to get rid of it would be to inspect the searchText for a potential date string before creating the expression and work with the date instead.

Expression<Func<Contact, bool>> cntExpression;

var searchDate = default(DateTime);
if (DateTime.TryParse(searchText.Trim(), out searchDate)) 
{
    cntExpression = p => p.DOB.HasValue && p.DOB == searchDate;
} 
else 
{
    cntExpression = p => p.LastName.ToLower().Trim().Contains(searchedText) ||
            p.FirstName.ToLower().Trim().Contains(searchedText) ||
            p.MiddleName.ToLower().Trim().Contains(searchedText) ||
            p.NickName.ToLower().Trim().Contains(searchedText);
}
2
9/3/2015 8:26:30 AM

Popular Answer

I solved this issue by changing my expression to:

            Expression<Func<Contact, bool>> cntExpression = p => p.LastName.ToLower().Trim().Contains(searchedText) ||
                p.FirstName.ToLower().Trim().Contains(searchedText) ||
                p.MiddleName.ToLower().Trim().Contains(searchedText) ||
                p.NickName.ToLower().Trim().Contains(searchedText) ||
                p.DriversLicenseNumber.ToLower().Trim().Contains(searchedText) ||
                (p.FirstName + " " + p.LastName).ToLower().Trim().Contains(searchedText);

            var searchDate = default(DateTime);
            if (DateTime.TryParse(searchedText.Trim(), out searchDate))
                cntExpression = cntExpression.And(p => p.DOB.HasValue && p.DOB == searchDate);

No error occurs now and code is exucuting properly.



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