Lambda动态创建

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Linq.Expressions; namespace ExpressionToSql
{
public class LambdaHelper
{
/// <summary>
/// Id等于
/// </summary>
/// <param name="Id"></param>
/// <returns></returns>
public Func<Model, bool> CreateFilterID(int Id)
{
ParameterExpression obj = Expression.Parameter(typeof(Model), "obj"); ConstantExpression constant = Expression.Constant(Id); MemberExpression member = Expression.PropertyOrField(obj, "Id"); BinaryExpression query = Expression.Equal(member, constant); var lambda = Expression.Lambda<Func<Model, bool>>(query, obj); var func = lambda.Compile();
return func;
} /// <summary>
/// Model等于
/// </summary>
/// <param name="model"></param>
/// <returns></returns>
public Func<Model, bool> CreateFilterModel(Model model)
{
ParameterExpression obj = Expression.Parameter(typeof(Model), "obj"); ConstantExpression constant = Expression.Constant(model.Id); MemberExpression member = Expression.PropertyOrField(obj, "Id"); BinaryExpression query = Expression.Equal(member, constant); var lambda = Expression.Lambda<Func<Model, bool>>(query, obj); var func = lambda.Compile();
return func;
} /// <summary>
/// Object 等于(1参数)
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="model"></param>
/// <returns></returns>
public Func<T, bool> CreateFilterObject<T>(T model) where T : class,new()
{
ParameterExpression obj = Expression.Parameter(typeof(T), "obj"); var constVal = Convert.ToInt32(GetPropertyValue(model, "Id"));
ConstantExpression constant = Expression.Constant(constVal); MemberExpression member = Expression.PropertyOrField(obj, "Id"); BinaryExpression query = Expression.Equal(member, constant); var lambda = Expression.Lambda<Func<T, bool>>(query, obj); var func = lambda.Compile();
return func;
} /// <summary>
/// Model等于(2参数)
/// </summary>
/// <returns></returns>
public Func<Model, Model, bool> CreateModelEqual()
{
ParameterExpression obj = Expression.Parameter(typeof(Model), "obj"); ParameterExpression obj1 = Expression.Parameter(typeof(Model), "obj1"); MemberExpression member = Expression.PropertyOrField(obj, "Id"); MemberExpression member1 = Expression.PropertyOrField(obj1, "Id"); BinaryExpression query = Expression.Equal(member, member1); var lambda = Expression.Lambda<Func<Model, Model, bool>>(query, obj, obj1); var func = lambda.Compile();
return func;
} /// <summary>
/// Int 等于
/// </summary>
/// <returns></returns>
public Func<int, int, bool> CreateIntEqual()
{
ParameterExpression member = Expression.Parameter(typeof(int), "id"); ParameterExpression val = Expression.Parameter(typeof(int), "val"); BinaryExpression bin = Expression.Equal(member, val); var lambda = Expression.Lambda<Func<int, int, bool>>(bin, member, val); var func = lambda.Compile();
return func;
} #region Extend private object GetPropertyValue<T>(T model, string proertyName)
where T : class
{
return model.GetType().GetProperty(proertyName).GetValue(model);
}
#endregion } public class Model
{
public int Id { get; set; }
public string Name { get; set; }
}
}
static void TestLambda()
{ LambdaHelper helper = new LambdaHelper(); Model test1 = new Model() { Id = , Name = "lcc1" };
Model test2 = new Model() { Id = , Name = "lcc2" };
Model test3 = new Model() { Id = , Name = "lcc3" }; List<Model> list = new List<Model>() { test1, test2, test3 }; //CreateFilterID
Console.WriteLine("-----------------CreateFilterID--------------------------");
var filterFunc = helper.CreateFilterID(); Console.WriteLine("test1中的Id 等于1:" + filterFunc(test1));
Console.WriteLine("test2中的Id 等于1:" + filterFunc(test1)); //CreateFilterModel
Console.WriteLine("--------------------CreateFilterModel---------------------");
var filterModelFunc = helper.CreateFilterModel(test1);
Console.WriteLine("test1中的等于test1:" + filterModelFunc(test1));
Console.WriteLine("test1中的等于test2:" + filterModelFunc(test2));
Console.WriteLine("list中的等于test1的数量:" + list.Where(filterModelFunc).Count()); //CreateFilterObject
Console.WriteLine("----------------------CreateFilterObject--------------------");
var filterObjectlFunc = helper.CreateFilterObject(test2);
Console.WriteLine("test2中的等于test1:" + filterObjectlFunc(test1));
Console.WriteLine("test2中的等于test2:" + filterObjectlFunc(test2)); Console.WriteLine("list中的等于test2的数量:" + list.Where(filterObjectlFunc).Count()); //CreateModelEqual
Console.WriteLine("-------------------CreateModelEqual--------------------------");
var modelEqualFunc = helper.CreateModelEqual(); Console.WriteLine("test1,test2是否相等:" + modelEqualFunc(test1, test2));
Console.WriteLine("test1,test1是否相等:" + modelEqualFunc(test1, test2)); //CreateIntEqual
Console.WriteLine("-----------------CreateIntEqual------------------------------");
var intEqualFunc = helper.CreateIntEqual();
Console.WriteLine("1,2是否相等:" + intEqualFunc(, ));
Console.WriteLine("1,1是否相等:" + intEqualFunc(, )); Console.Read(); }

Lambda动态创建

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