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