Dynamic Expression Building Error

Question

I have searched a lot regarding this issue what is wrong here

Shorter version of my code is
/// companyid  is integer type value here is 220
    var cond1 = BuildExpression(companyId);
    var acntlst=entities.Accounts.Where(cond).ToList();

Account is a class querying against Account collection

BuildExpression function

 private static Expression<Func<Account, bool>> BuildExpression(string companyid)

 {
    var paramexp = Expression.Parameter(typeof (Account), "p");
     var proprty = typeof(Account).GetProperty("CompanyId");
     var prpexp = Expression.Property(paramexp, proprty);

     var varexp = Expression.Variable(typeof(Int32), companyid);
     var cond1 = Expression.Equal(prpexp, varexp);

     return Expression.Lambda<Func<Account, bool>>(cond1,paramexp);
    }

Error message is

The parameter '220' was not bound in the specified LINQ to Entities query expression

SLaks · Accepted Answer · 2013-08-26 14:15:10Z

3

Expression.Variable(typeof(Int32), companyid);

This creates a variable named "220".
You never declared this variable or assigned it a value.

Instead, you want Expression.Constant, which takes a value and returns an expression which has that value.
(you will probably need to parse the string into an int)

However, you don't need to build this by hand at all.

Instead, you should just write return a => a.CompanyId == companyId

answered Aug 26, 2013 at 14:15

SLaks

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