I am looking to implement a system whereby a use that 'build' conditions and then return the resulting data back from the database. At present, there is a stored procedure which generates SQL on the fly and executes it. This is a particular issue that I want to remove.
My problem is coming from the fact that I can have multiple fields within my criteria, and for each of these fields, there could be 1 or more values, with different potential operators.
For example,
from t in Contacts
where t.Email == "email@domain.com" || t.Email.Contains ("mydomain")
where t.Field1 == "valuewewant"
where t.Field2 != "valuewedontwant"
select t
List<FieldCriteria>
Email, Equals, "email@domain.com"
Email, Contains, "mydomain" Field1,
Equals, "valuewewant" Field2,
DoesNotEqual, "valuewedontwant"
new FieldCriteria
{
FieldName = "Email",
Operator = 1,
Value = "email@mydomain.com"
}
enum Operator
{
Equals = 1,
}
class Condition
{
public string Field { get; set; }
public Operator Operator { get; set;}
public string Value { get; set;}
}
void Main()
{
var conditions = new List<Condition>();
conditions.Add(new Condition {
Field = "Email",
Operator = Operator.Equals,
Value = "email1@domain.com"
});
conditions.Add(new Condition {
Field = "Email",
Operator = Operator.Equals,
Value = "email2@domain.com"
});
conditions.Add(new Condition {
Field = "Field1",
Operator = Operator.Equals,
Value = "Chris"
});
var statusConditions = "Status = 1";
var emailConditions = from c in conditions where c.Field == "Email" select c;
var field1Conditions = from c in conditions where c.Field == "Field1" select c;
var emailConditionsFormatted = from c in emailConditions select string.Format("Email=\"{0}\"", c.Value);
var field1ConditionsFormatted = from c in field1Conditions select string.Format("Field1=\"{0}\"", c.Value);
string[] conditionsArray = emailConditionsFormatted.ToArray();
var emailConditionsJoined = string.Join("||", conditionsArray);
Console.WriteLine(String.Format("Formatted Condition For Email: {0}",emailConditionsJoined));
conditionsArray = field1ConditionsFormatted.ToArray();
var field1ConditionsJoined = string.Join("||", conditionsArray);
Console.WriteLine(String.Format("Formatted Condition For Field1: {0}",field1ConditionsJoined));
IQueryable results = ContactView.Where(statusConditions);
if (emailConditions != null)
{
results = results.Where(emailConditionsJoined);
}
if (field1Conditions != null)
{
results = results.Where(field1ConditionsJoined);
}
results = results.Select("id");
foreach (int id in results)
{
Console.WriteLine(id.ToString());
}
}
-- Region Parameters
DECLARE @p0 VarChar(1000) = 'Chris'
DECLARE @p1 VarChar(1000) = 'email1@domain.com'
DECLARE @p2 VarChar(1000) = 'email2@domain.com'
DECLARE @p3 Int = 1
-- EndRegion
SELECT [t0].[id]
FROM [Contacts].[ContactView] AS [t0]
WHERE ([t0].[field1] = @p0) AND (([t0].[email] = @p1) OR ([t0].[email] = @p2)) AND ([t0].[status] = @p3)
Formatted Condition For Email: Email="email1@domain.com"||Email="email2@domain.com"
Formatted Condition For Field1: Field1="Chris"
I think Dynamic LINQ will be one of option. DLINQ allows you to specify part of the LINQ query as "string" and DLINQ then compiles that string to Expression tree so that be passed to the underlying LINQ provider. Your need is also same i.e you need to create Expression trees at runtime.
I would suggest you to make the property Operator
in FieldCriteria
as an Enum
which represent all the required operations (equals, less then etc). Then you will need to write a function that takes a list of FieldCriteria
and return a "expression" string which then can be fed into DLINQ to get the expression tree.