（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; if (p.page <= 0) { p.page = 1; } if (p.rows <= 0) { p.rows = 10; } var data = manage.GetQueryable().Select(d => d); //过滤 data = data.Where(p.filters); //搜索条件 if (query != null && query.Length > 0) { 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 - 1) * 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。
1 using System; 2 using System.Collections.Generic; 3 using System.Linq; 4 using System.Linq.Expressions; 5 using System.Reflection; 6 using System.Web; 7 using Vegetable.Models; 8 9 namespace Vegetable.DAL 10 { 11 public static class QueryableExtension 12 { 13 14 public static IQueryable<T> OrderBy<T>(this IQueryable<T> source, string[] propertyName, bool[] ascending) where T : class 15 { 16 Type type = typeof(T); 17 18 for (int i = 0; i < propertyName.Length; i++) 19 { 20 21 PropertyInfo property = type.GetProperty(propertyName[i]); 22 if (property == null) 23 throw new ArgumentException("propertyName", "Not Exist"); 24 25 ParameterExpression param = Expression.Parameter(type, "p"); 26 Expression propertyAccessExpression = Expression.MakeMemberAccess(param, property); 27 LambdaExpression orderByExpression = Expression.Lambda(propertyAccessExpression, param); 28 29 string methodName = ascending[i] ? "OrderBy" : "OrderByDescending"; 30 if (i != 0) 31 { 32 methodName = ascending[i] ? "ThenBy" : "ThenByDescending"; 33 } 34 35 MethodCallExpression resultExp = Expression.Call(typeof(Queryable), methodName, new Type[] { type, property.PropertyType }, source.Expression, Expression.Quote(orderByExpression)); 36 source = source.Provider.CreateQuery<T>(resultExp); 37 38 } 39 40 41 return source; 42 } 43 44 45 public static IQueryable<T> Where<T>(this IQueryable<T> source, FilterRule[] filterRules) where T : class 46 { 47 if (filterRules == null) 48 { 49 return source; 50 } 51 Type type = typeof(T); 52 53 ParameterExpression param = Expression.Parameter(type, "c"); 54 55 Expression<Func<T, bool>> op = null; 56 57 foreach (var rule in filterRules) 58 { 59 PropertyInfo property = type.GetProperty(rule.Field); 60 if (property == null) 61 { 62 continue; 63 } 64 //c.Field==Value 65 //c=>c.Field.Contains(Value) 66 Expression left = Expression.Property(param, property); 67 68 Expression right = Expression.Constant(rule.Value); 69 Type valueType = property.PropertyType; 70 if (rule.Value == null || rule.Value == "") continue; 71 DateTime inputDateTime = DateTime.Now; 72 try 73 { 74 75 if (valueType == typeof(int) || valueType == typeof(int?)) 76 { 77 right = Expression.Constant(Convert.ToInt32(rule.Value.Split('.')[0])); 78 } 79 else if (valueType == typeof(short) || valueType == typeof(short?)) 80 { 81 right = Expression.Constant(Convert.ToInt16(rule.Value.Split('.')[0])); 82 } 83 else if (valueType == typeof(byte) || valueType == typeof(byte?)) 84 { 85 right = Expression.Constant(Convert.ToByte(rule.Value.Split('.')[0])); 86 } 87 else if (valueType == typeof(long) || valueType == typeof(long?)) 88 { 89 right = Expression.Constant(Convert.ToInt64(rule.Value)); 90 } 91 else if (valueType == typeof(float) || valueType == typeof(float?)) 92 { 93 right = Expression.Constant(Convert.ToSingle(rule.Value)); 94 } 95 else if (valueType == typeof(double) || valueType == typeof(double?)) 96 { 97 right = Expression.Constant(Convert.ToDouble(rule.Value)); 98 } 99 else if (valueType == typeof(decimal) || valueType == typeof(decimal?)) 100 { 101 right = Expression.Constant(Convert.ToDecimal(rule.Value)); 102 } 103 else if (valueType == typeof(DateTime) || valueType == typeof(DateTime?)) 104 { 105 inputDateTime = Convert.ToDateTime(rule.Value); 106 right = Expression.Constant(Convert.ToDateTime(rule.Value)); 107 } 108 else if (valueType == typeof(Guid) || valueType == typeof(Guid?)) 109 { 110 right = Expression.Constant(Guid.Parse(rule.Value)); 111 } 112 113 } 114 catch (Exception ex) 115 { 116 Console.WriteLine(ex.Message); 117 break; 118 } 119 120 121 Expression filter = Expression.Equal(left, right); 122 Expression filter2 = null; 123 MethodInfo method; 124 125 switch (rule.Op) 126 { 127 case OP.contains: 128 //BinaryExpression 129 if (valueType == typeof(string)) 130 { 131 method = typeof(string).GetMethod("Contains", new[] { typeof(string) }); 132 filter = Expression.Call(left, method, right); 133 } 134 else if (valueType == typeof(DateTime) || valueType == typeof(DateTime?)) 135 { 136 right = Expression.Constant(inputDateTime.Date); 137 filter = Expression.GreaterThanOrEqual(left, right); 138 right = Expression.Constant(inputDateTime.Date.AddDays(1)); 139 filter2 = Expression.LessThan(left, right); 140 } 141 else 142 { 143 filter = Expression.Equal(left, right); 144 } 145 break; 146 case OP.equal: 147 filter = Expression.Equal(left, right); 148 break; 149 case OP.notequal: 150 filter = Expression.NotEqual(left, right); 151 break; 152 case OP.beginwith: 153 method = typeof(string).GetMethod("StartsWith", new[] { typeof(string) }); 154 155 filter = Expression.Call(left, method, right); 156 break; 157 case OP.endwith: 158 method = typeof(string).GetMethod("EndsWith", new[] { typeof(string) }); 159 160 filter = Expression.Call(left, method, right); 161 break; 162 case OP.less: 163 filter = Expression.LessThan(left, right); 164 break; 165 case OP.lessorequal: 166 filter = Expression.LessThanOrEqual(left, right); 167 break; 168 case OP.greater: 169 filter = Expression.GreaterThan(left, right); 170 break; 171 case OP.greaterorequal: 172 filter = Expression.GreaterThanOrEqual(left, right); 173 break; 174 default: 175 break; 176 } 177 178 179 180 var lambda = Expression.Lambda<Func<T, bool>>(filter, param); 181 if (op == null) 182 { 183 op = lambda; 184 } 185 else 186 { 187 op = Expression.Lambda<Func<T, bool>>(Expression.And(op.Body, lambda.Body), op.Parameters); 188 } 189 190 if (filter2 != null) 191 { 192 var lambda2 = Expression.Lambda<Func<T, bool>>(filter2, param); 193 op = Expression.Lambda<Func<T, bool>>(Expression.And(op.Body, lambda2.Body), op.Parameters); 194 } 195 } 196 197 if (op != null) 198 { 199 source = source.Where(op); 200 } 201 return source; 202 } 203 204 205 public static IQueryable<T> Where<T>(this IQueryable<T> source, Filter[] filters) where T : class 206 { 207 if (filters == null) 208 { 209 return source; 210 } 211 Type type = typeof(T); 212 213 ParameterExpression param = Expression.Parameter(type, "c"); 214 215 Expression<Func<T, bool>> op = null; 216 217 218 foreach (var rule in filters) 219 { 220 PropertyInfo property = type.GetProperty(rule.Field); 221 if (property == null) 222 { 223 continue; 224 } 225 //c.Field==Value 226 //c=>(c.Field.Contains(Value) || c.Field.Contains(Value)) 227 Exception outExc = new Exception(); 228 229 Expression left = Expression.Property(param, property); 230 Type valueType = property.PropertyType; 231 if (rule.Value == null || rule.Value.Length <= 0) continue; 232 233 Expression<Func<T, bool>> lambdaOut = null; 234 foreach (var v in rule.Value) 235 { 236 Expression right = Expression.Constant(v); 237 DateTime inputDateTime = DateTime.Now; 238 try 239 { 240 241 if (valueType == typeof(int) || valueType == typeof(int?)) 242 { 243 right = Expression.Constant(Convert.ToInt32(v.Split('.')[0])); 244 } 245 else if (valueType == typeof(short) || valueType == typeof(short?)) 246 { 247 right = Expression.Constant(Convert.ToInt16(v.Split('.')[0])); 248 } 249 else if (valueType == typeof(byte) || valueType == typeof(byte?)) 250 { 251 right = Expression.Constant(Convert.ToByte(v.Split('.')[0])); 252 } 253 else if (valueType == typeof(long) || valueType == typeof(long?)) 254 { 255 right = Expression.Constant(Convert.ToInt64(v)); 256 } 257 else if (valueType == typeof(float) || valueType == typeof(float?)) 258 { 259 right = Expression.Constant(Convert.ToSingle(v)); 260 } 261 else if (valueType == typeof(double) || valueType == typeof(double?)) 262 { 263 right = Expression.Constant(Convert.ToDouble(v)); 264 } 265 else if (valueType == typeof(decimal) || valueType == typeof(decimal?)) 266 { 267 right = Expression.Constant(Convert.ToDecimal(v)); 268 } 269 else if (valueType == typeof(DateTime) || valueType == typeof(DateTime?)) 270 { 271 inputDateTime = Convert.ToDateTime(v); 272 right = Expression.Constant(Convert.ToDateTime(v)); 273 } 274 else if (valueType == typeof(Guid) || valueType == typeof(Guid?)) 275 { 276 right = Expression.Constant(Guid.Parse(v)); 277 } 278 279 } 280 catch (Exception ex) 281 { 282 Console.WriteLine(ex.Message); 283 break; 284 } 285 286 287 Expression filter = Expression.Equal(left, right); 288 Expression filter2 = null; 289 MethodInfo method; 290 291 switch (rule.Op) 292 { 293 case OP.contains: 294 //BinaryExpression 295 if (valueType == typeof(string)) 296 { 297 method = typeof(string).GetMethod("Contains", new[] { typeof(string) }); 298 filter = Expression.Call(left, method, right); 299 } 300 else if (valueType == typeof(DateTime) || valueType == typeof(DateTime?)) 301 { 302 right = Expression.Constant(inputDateTime.Date); 303 filter = Expression.GreaterThanOrEqual(left, right); 304 right = Expression.Constant(inputDateTime.Date.AddDays(1)); 305 filter2 = Expression.LessThan(left, right); 306 } 307 else 308 { 309 filter = Expression.Equal(left, right); 310 } 311 break; 312 case OP.equal: 313 filter = Expression.Equal(left, right); 314 break; 315 case OP.notequal: 316 filter = Expression.NotEqual(left, right); 317 break; 318 case OP.beginwith: 319 method = typeof(string).GetMethod("StartsWith", new[] { typeof(string) }); 320 321 filter = Expression.Call(left, method, right); 322 break; 323 case OP.endwith: 324 method = typeof(string).GetMethod("EndsWith", new[] { typeof(string) }); 325 326 filter = Expression.Call(left, method, right); 327 break; 328 case OP.less: 329 filter = Expression.LessThan(left, right); 330 break; 331 case OP.lessorequal: 332 filter = Expression.LessThanOrEqual(left, right); 333 break; 334 case OP.greater: 335 filter = Expression.GreaterThan(left, right); 336 break; 337 case OP.greaterorequal: 338 filter = Expression.GreaterThanOrEqual(left, right); 339 break; 340 default: 341 break; 342 } 343 344 345 346 var lambda = Expression.Lambda<Func<T, bool>>(filter, param); 347 if (lambdaOut == null) 348 { 349 lambdaOut = lambda; 350 } 351 else 352 { 353 lambdaOut = Expression.Lambda<Func<T, bool>>(Expression.Or(lambdaOut.Body, lambda.Body), lambdaOut.Parameters); 354 } 355 356 if (filter2 != null) 357 { 358 var lambda2 = Expression.Lambda<Func<T, bool>>(filter2, param); 359 lambdaOut = Expression.Lambda<Func<T, bool>>(Expression.And(lambdaOut.Body, lambda2.Body), lambdaOut.Parameters); 360 } 361 } 362 if (op == null) 363 { 364 op = lambdaOut; 365 } 366 else 367 { 368 op = Expression.Lambda<Func<T, bool>>(Expression.And(op.Body, lambdaOut.Body), op.Parameters); 369 } 370 371 } 372 if (op != null) 373 { 374 source = source.Where(op); 375 } 376 return source; 377 378 } 379 380 public static IQueryable<T> Where<T>(this IQueryable<T> source, string[] columnNames, string filterString) 381 { 382 383 Type type = typeof(T); 384 385 ParameterExpression param = Expression.Parameter(type, "c"); 386 387 Expression right = Expression.Constant(filterString); 388 389 //1!=1 390 //Expression op = Expression.NotEqual(Expression.Constant(1), Expression.Constant(1)); 391 Expression<Func<T, bool>> op = null; 392 393 394 foreach (var column in columnNames) 395 { 396 PropertyInfo property = type.GetProperty(column); 397 if (property == null) 398 { 399 continue; 400 } 401 //c.Field==Value 402 //c=>c.Field.Contains(Value) 403 Expression left = Expression.Property(param, property); 404 405 Type valueType = property.PropertyType; 406 if (valueType != typeof(string)) continue; 407 if (filterString == null || filterString == "") continue; 408 409 410 MethodInfo method = typeof(string).GetMethod("Contains", new[] { typeof(string) }); 411 412 413 Expression filter = Expression.Call(left, method, right); 414 415 var lambda = Expression.Lambda<Func<T, bool>>(filter, param); 416 if (op == null) 417 { 418 op = lambda; 419 } 420 else 421 { 422 423 op = Expression.Lambda<Func<T, bool>>(Expression.Or(op.Body, lambda.Body), op.Parameters); 424 } 425 } 426 427 if (op != null) 428 { 429 430 source = source.Where(op); 431 } 432 return source; 433 } 434 } 435 }