dotnet-dynamic-linq/PoweredSoft.DynamicLinq/Helpers/QueryableHelpers.cs

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2018-02-11 20:55:29 -05:00
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Text;
using System.Threading.Tasks;
namespace PoweredSoft.DynamicLinq.Helpers
{
public static class QueryableHelpers
{
public static Expression GetConditionExpressionForMember(ParameterExpression parameter, Expression member, ConditionOperators conditionOperator, ConstantExpression constant)
{
if (parameter == null)
throw new ArgumentNullException("parameter");
if (member == null)
throw new ArgumentNullException("member");
if (constant == null)
throw new ArgumentNullException("constant");
Expression ret = null;
if (conditionOperator == ConditionOperators.Equal)
ret = Expression.Equal(member, constant);
else if (conditionOperator == ConditionOperators.GreaterThan)
ret = Expression.GreaterThan(member, constant);
else if (conditionOperator == ConditionOperators.GreaterThanOrEqual)
ret = Expression.GreaterThanOrEqual(member, constant);
else if (conditionOperator == ConditionOperators.LessThan)
ret = Expression.LessThan(member, constant);
else if (conditionOperator == ConditionOperators.LessThanOrEqual)
ret = Expression.LessThanOrEqual(member, constant);
else if (conditionOperator == ConditionOperators.Contains)
ret = Expression.Call(member, Constants.ContainsMethod, constant);
else if (conditionOperator == ConditionOperators.StartsWith)
ret = Expression.Call(member, Constants.StartsWithMethod, constant);
else if (conditionOperator == ConditionOperators.EndsWith)
ret = Expression.Call(member, Constants.EndsWithMethod, constant);
else
throw new ArgumentException("conditionOperator", "Must supply a known condition operator");
return ret;
}
/// <summary>
/// Returns the right expression for a path supplied.
/// </summary>
/// <param name="param">Expression.Parameter(typeOfClassOrInterface)</param>
/// <param name="path">the path you wish to resolve example Contact.Profile.FirstName</param>
/// <returns></returns>
public static Expression ResolvePathForExpression(ParameterExpression param, string path)
{
Expression body = param;
foreach (var member in path.Split('.'))
{
body = Expression.PropertyOrField(body, member);
}
return body;
}
public static ConstantExpression GetConstantSameAsLeftOperator(Expression member, object value)
{
if (member == null)
throw new ArgumentNullException("member");
if (value == null)
return Expression.Constant(null);
// the types.
var valueType = value.GetType();
var memberType = member.Type;
// if match.
if (valueType == memberType)
return Expression.Constant(value);
// attempt a conversion.
object convertedValue = TypeHelpers.ConvertFrom(memberType, value);
return Expression.Constant(convertedValue);
}
}
}