EF 拉姆达 linq 帮助类
（这个类是很早以前在网上找的，忘记出处请原谅。）
一、基本用法
[Route("List")]
public ApiResult GetList(int page, int limit, string sort = null, string order = null, string filters = null, string query = null)
{
PageModel p = new PageModel();
if (filters != null)
{
p.filters = Newtonsoft.Json.JsonConvert.DeserializeObject<Filter[]>(filters);
}
p.page = page;
p.rows = limit;
p.sort = sort;
p.order = order;
)
{
p.page = ;
}
)
{
p.rows = ;
}
var data = manage.GetQueryable().Select(d => d);
//过滤
data = data.Where(p.filters);
//搜索条件
)
{
data = data.Where(new string[] { "UserName", "RealName" }, query);
}
//排序
if (order != "normal" && sort != null)
{
bool isAsc = order == "asc";
data = data.OrderBy(new[] { sort }, new[] { isAsc });
}
else
{
//默认排序
data = data.OrderBy(d => d.UserID);
}
DataModel pageData = new DataModel();
pageData.page = p.page;
pageData.total = data.Count();
pageData.rows = data.Skip((p.page - ) * p.rows).Take(p.rows).ToList();
ApiResult result = new ApiResult();
result.success = true;
result.data = pageData;
return result;
}
完整案例：结合前端 elementUI 组件 可以实现分页 查询、排序、过滤等。
https://www.cnblogs.com/hao-1234-1234/p/9647322.html#4225885
二、linq 帮助类
重写了where和orderby方法。
using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;
using System.Web;
using Vegetable.Models;
namespace Vegetable.DAL
{
public static class QueryableExtension
{
public static IQueryable<T> OrderBy<T>(this IQueryable<T> source, string[] propertyName, bool[] ascending) where T : class
{
Type type = typeof(T);
; i < propertyName.Length; i++)
{
PropertyInfo property = type.GetProperty(propertyName[i]);
if (property == null)
throw new ArgumentException("propertyName", "Not Exist");
ParameterExpression param = Expression.Parameter(type, "p");
Expression propertyAccessExpression = Expression.MakeMemberAccess(param, property);
LambdaExpression orderByExpression = Expression.Lambda(propertyAccessExpression, param);
string methodName = ascending[i] ? "OrderBy" : "OrderByDescending";
)
{
methodName = ascending[i] ? "ThenBy" : "ThenByDescending";
}
MethodCallExpression resultExp = Expression.Call(typeof(Queryable), methodName, new Type[] { type, property.PropertyType }, source.Expression, Expression.Quote(orderByExpression));
source = source.Provider.CreateQuery<T>(resultExp);
}
return source;
}
public static IQueryable<T> Where<T>(this IQueryable<T> source, FilterRule[] filterRules) where T : class
{
if (filterRules == null)
{
return source;
}
Type type = typeof(T);
ParameterExpression param = Expression.Parameter(type, "c");
Expression<Func<T, bool>> op = null;
foreach (var rule in filterRules)
{
PropertyInfo property = type.GetProperty(rule.Field);
if (property == null)
{
continue;
}
//c.Field==Value
//c=>c.Field.Contains(Value)
Expression left = Expression.Property(param, property);
Expression right = Expression.Constant(rule.Value);
Type valueType = property.PropertyType;
if (rule.Value == null || rule.Value == "") continue;
DateTime inputDateTime = DateTime.Now;
try
{
if (valueType == typeof(int) || valueType == typeof(int?))
{
right = Expression.Constant(Convert.ToInt32(rule.Value.Split(]));
}
else if (valueType == typeof(short) || valueType == typeof(short?))
{
right = Expression.Constant(Convert.ToInt16(rule.Value.Split(]));
}
else if (valueType == typeof(byte) || valueType == typeof(byte?))
{
right = Expression.Constant(Convert.ToByte(rule.Value.Split(]));
}
else if (valueType == typeof(long) || valueType == typeof(long?))
{
right = Expression.Constant(Convert.ToInt64(rule.Value));
}
else if (valueType == typeof(float) || valueType == typeof(float?))
{
right = Expression.Constant(Convert.ToSingle(rule.Value));
}
else if (valueType == typeof(double) || valueType == typeof(double?))
{
right = Expression.Constant(Convert.ToDouble(rule.Value));
}
else if (valueType == typeof(decimal) || valueType == typeof(decimal?))
{
right = Expression.Constant(Convert.ToDecimal(rule.Value));
}
else if (valueType == typeof(DateTime) || valueType == typeof(DateTime?))
{
inputDateTime = Convert.ToDateTime(rule.Value);
right = Expression.Constant(Convert.ToDateTime(rule.Value));
}
else if (valueType == typeof(Guid) || valueType == typeof(Guid?))
{
right = Expression.Constant(Guid.Parse(rule.Value));
}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
break;
}
Expression filter = Expression.Equal(left, right);
Expression filter2 = null;
MethodInfo method;
switch (rule.Op)
{
case OP.contains:
//BinaryExpression
if (valueType == typeof(string))
{
method = typeof(string).GetMethod("Contains", new[] { typeof(string) });
filter = Expression.Call(left, method, right);
}
else if (valueType == typeof(DateTime) || valueType == typeof(DateTime?))
{
right = Expression.Constant(inputDateTime.Date);
filter = Expression.GreaterThanOrEqual(left, right);
right = Expression.Constant(inputDateTime.Date.AddDays());
filter2 = Expression.LessThan(left, right);
}
else
{
filter = Expression.Equal(left, right);
}
break;
case OP.equal:
filter = Expression.Equal(left, right);
break;
case OP.notequal:
filter = Expression.NotEqual(left, right);
break;
case OP.beginwith:
method = typeof(string).GetMethod("StartsWith", new[] { typeof(string) });
filter = Expression.Call(left, method, right);
break;
case OP.endwith:
method = typeof(string).GetMethod("EndsWith", new[] { typeof(string) });
filter = Expression.Call(left, method, right);
break;
case OP.less:
filter = Expression.LessThan(left, right);
break;
case OP.lessorequal:
filter = Expression.LessThanOrEqual(left, right);
break;
case OP.greater:
filter = Expression.GreaterThan(left, right);
break;
case OP.greaterorequal:
filter = Expression.GreaterThanOrEqual(left, right);
break;
default:
break;
}
var lambda = Expression.Lambda<Func<T, bool>>(filter, param);
if (op == null)
{
op = lambda;
}
else
{
op = Expression.Lambda<Func<T, bool>>(Expression.And(op.Body, lambda.Body), op.Parameters);
}
if (filter2 != null)
{
var lambda2 = Expression.Lambda<Func<T, bool>>(filter2, param);
op = Expression.Lambda<Func<T, bool>>(Expression.And(op.Body, lambda2.Body), op.Parameters);
}
}
if (op != null)
{
source = source.Where(op);
}
return source;
}
public static IQueryable<T> Where<T>(this IQueryable<T> source, Filter[] filters) where T : class
{
if (filters == null)
{
return source;
}
Type type = typeof(T);
ParameterExpression param = Expression.Parameter(type, "c");
Expression<Func<T, bool>> op = null;
foreach (var rule in filters)
{
PropertyInfo property = type.GetProperty(rule.Field);
if (property == null)
{
continue;
}
//c.Field==Value
//c=>(c.Field.Contains(Value) || c.Field.Contains(Value))
Exception outExc = new Exception();
Expression left = Expression.Property(param, property);
Type valueType = property.PropertyType;
) continue;
Expression<Func<T, bool>> lambdaOut = null;
foreach (var v in rule.Value)
{
Expression right = Expression.Constant(v);
DateTime inputDateTime = DateTime.Now;
try
{
if (valueType == typeof(int) || valueType == typeof(int?))
{
right = Expression.Constant(Convert.ToInt32(v.Split(]));
}
else if (valueType == typeof(short) || valueType == typeof(short?))
{
right = Expression.Constant(Convert.ToInt16(v.Split(]));
}
else if (valueType == typeof(byte) || valueType == typeof(byte?))
{
right = Expression.Constant(Convert.ToByte(v.Split(]));
}
else if (valueType == typeof(long) || valueType == typeof(long?))
{
right = Expression.Constant(Convert.ToInt64(v));
}
else if (valueType == typeof(float) || valueType == typeof(float?))
{
right = Expression.Constant(Convert.ToSingle(v));
}
else if (valueType == typeof(double) || valueType == typeof(double?))
{
right = Expression.Constant(Convert.ToDouble(v));
}
else if (valueType == typeof(decimal) || valueType == typeof(decimal?))
{
right = Expression.Constant(Convert.ToDecimal(v));
}
else if (valueType == typeof(DateTime) || valueType == typeof(DateTime?))
{
inputDateTime = Convert.ToDateTime(v);
right = Expression.Constant(Convert.ToDateTime(v));
}
else if (valueType == typeof(Guid) || valueType == typeof(Guid?))
{
right = Expression.Constant(Guid.Parse(v));
}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
break;
}
Expression filter = Expression.Equal(left, right);
Expression filter2 = null;
MethodInfo method;
switch (rule.Op)
{
case OP.contains:
//BinaryExpression
if (valueType == typeof(string))
{
method = typeof(string).GetMethod("Contains", new[] { typeof(string) });
filter = Expression.Call(left, method, right);
}
else if (valueType == typeof(DateTime) || valueType == typeof(DateTime?))
{
right = Expression.Constant(inputDateTime.Date);
filter = Expression.GreaterThanOrEqual(left, right);
right = Expression.Constant(inputDateTime.Date.AddDays());
filter2 = Expression.LessThan(left, right);
}
else
{
filter = Expression.Equal(left, right);
}
break;
case OP.equal:
filter = Expression.Equal(left, right);
break;
case OP.notequal:
filter = Expression.NotEqual(left, right);
break;
case OP.beginwith:
method = typeof(string).GetMethod("StartsWith", new[] { typeof(string) });
filter = Expression.Call(left, method, right);
break;
case OP.endwith:
method = typeof(string).GetMethod("EndsWith", new[] { typeof(string) });
filter = Expression.Call(left, method, right);
break;
case OP.less:
filter = Expression.LessThan(left, right);
break;
case OP.lessorequal:
filter = Expression.LessThanOrEqual(left, right);
break;
case OP.greater:
filter = Expression.GreaterThan(left, right);
break;
case OP.greaterorequal:
filter = Expression.GreaterThanOrEqual(left, right);
break;
default:
break;
}
var lambda = Expression.Lambda<Func<T, bool>>(filter, param);
if (lambdaOut == null)
{
lambdaOut = lambda;
}
else
{
lambdaOut = Expression.Lambda<Func<T, bool>>(Expression.Or(lambdaOut.Body, lambda.Body), lambdaOut.Parameters);
}
if (filter2 != null)
{
var lambda2 = Expression.Lambda<Func<T, bool>>(filter2, param);
lambdaOut = Expression.Lambda<Func<T, bool>>(Expression.And(lambdaOut.Body, lambda2.Body), lambdaOut.Parameters);
}
}
if (op == null)
{
op = lambdaOut;
}
else
{
op = Expression.Lambda<Func<T, bool>>(Expression.And(op.Body, lambdaOut.Body), op.Parameters);
}
}
if (op != null)
{
source = source.Where(op);
}
return source;
}
public static IQueryable<T> Where<T>(this IQueryable<T> source, string[] columnNames, string filterString)
{
Type type = typeof(T);
ParameterExpression param = Expression.Parameter(type, "c");
Expression right = Expression.Constant(filterString);
//1!=1
//Expression op = Expression.NotEqual(Expression.Constant(1), Expression.Constant(1));
Expression<Func<T, bool>> op = null;
foreach (var column in columnNames)
{
PropertyInfo property = type.GetProperty(column);
if (property == null)
{
continue;
}
//c.Field==Value
//c=>c.Field.Contains(Value)
Expression left = Expression.Property(param, property);
Type valueType = property.PropertyType;
if (valueType != typeof(string)) continue;
if (filterString == null || filterString == "") continue;
MethodInfo method = typeof(string).GetMethod("Contains", new[] { typeof(string) });
Expression filter = Expression.Call(left, method, right);
var lambda = Expression.Lambda<Func<T, bool>>(filter, param);
if (op == null)
{
op = lambda;
}
else
{
op = Expression.Lambda<Func<T, bool>>(Expression.Or(op.Body, lambda.Body), op.Parameters);
}
}
if (op != null)
{
source = source.Where(op);
}
return source;
}
}
}
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