灵活掌握Asp.net MVC中GridView的使用方法_实用技巧_

 public class Customer { public int Id { get; set; } public string CompanyName { get; set; } public string ContactTitle { get; set; } public string Address { get; set; } public string City { get; set; } public string Country { get; set; } public string Phone { get; set; } public DateTime Founded { get; set; } } 

 public class CustomersViewModel { public IQueryable Customers { get; set; } public PagingInfo PagingInfo { get; set; } public string JsonPagingInfo { get; set; } } 

 public static class ExpresssionBuilder { private static readonly MethodInfo containsMethod = typeof(string).GetMethod("Contains"); private static readonly MethodInfo startsWithMethod = typeof(string).GetMethod("StartsWith", new Type[] { typeof(string) }); private static readonly MethodInfo endsWithMethod = typeof(string).GetMethod("EndsWith", new Type[] { typeof(string) }); public static Expression> GetExpression(IList filters) { if (filters.Count == 0) return null; ParameterExpression param = Expression.Parameter(typeof(T), "t"); Expression exp = null; if (filters.Count == 1) exp = GetExpression(param, filters[0]); else if (filters.Count == 2) exp = GetExpression(param, filters[0], filters[1]); else { while (filters.Count > 0) { var f1 = filters[0]; var f2 = filters[1]; if (exp == null) exp = GetExpression(param, filters[0], filters[1]); else exp = Expression.AndAlso(exp, GetExpression(param, filters[0], filters[1])); filters.Remove(f1); filters.Remove(f2); if (filters.Count == 1) { exp = Expression.AndAlso(exp, GetExpression(param, filters[0])); filters.RemoveAt(0); } } } return Expression.Lambda>(exp, param); } private static Expression GetExpression(ParameterExpression param, FilterObject filter) { MemberExpression member = Expression.Property(param, filter.Column); //ConstantExpression constant = Expression.Constant(filter.Value); //新的逻辑来处理可空Decimal和DateTime值 UnaryExpression constant = null; if (member.Type == typeof(Decimal?)) { constant = Expression.Convert(Expression.Constant(Decimal.Parse(filter.Value)) , member.Type); } else if (member.Type == typeof(DateTime?)) { constant = Expression.Convert(Expression.Constant(DateTime.Parse(filter.Value)), member.Type); } else { constant = Expression.Convert(Expression.Constant(filter.Value), member.Type); } switch (filter.Operator) { case FilterOperator.Equals: return Expression.Equal(member, constant); case FilterOperator.GreaterThan: return Expression.GreaterThan(member, constant); case FilterOperator.GreaterThanOrEqual: return Expression.GreaterThanOrEqual(member, constant); case FilterOperator.LessThan: return Expression.LessThan(member, constant); case FilterOperator.LessThanOrEqual: return Expression.LessThanOrEqual(member, constant); case FilterOperator.Contains: return Expression.Call(member, containsMethod, constant); case FilterOperator.StartsWith: return Expression.Call(member, startsWithMethod, constant); case FilterOperator.EndsWith: return Expression.Call(member, endsWithMethod, constant); case FilterOperator.NotEqual: return Expression.Negate(Expression.Equal(member, constant)); } return null; } private static BinaryExpression GetExpression (ParameterExpression param, FilterObject filter1, FilterObject filter2) { Expression bin1 = GetExpression(param, filter1); Expression bin2 = GetExpression(param, filter2); return Expression.AndAlso(bin1, bin2); } } 

 public class PagingInfo { public List PageOptions { get; set; } public bool ShowPageOptions { get; set; } public int TotalItems { get; set; } public int ItemsPerPage { get; set; } public int CurrentPage { get; set; } public int TotalPages { get { return (int)Math.Ceiling((decimal)TotalItems / (ItemsPerPage != 0 ? ItemsPerPage : 1)); } } public SortObject Sort { get; set; } public IList Filters { get; set; } public string SearchTerm { get; set; } } public class SortObject { public String SortColumn { get; set; } public SortDirection Direction { get; set; } } public class FilterObject { public string Column { get; set; } public string Value { get; set; } public FilterOperator Operator { get; set; } public FilterConjunction Conjunction { get; set; } } /********* ENUMS *************/ public enum SortDirection { NotSet, Ascending, Descending } public enum FilterOperator { Contains, GreaterThan, GreaterThanOrEqual, LessThan, LessThanOrEqual, StartsWith, EndsWith, Equals, NotEqual } public enum FilterConjunction { And, Or } public class Extensions { public static string GetWhereClause(FilterObject filterObj, Type valueType) { string whereClause = "true"; if (valueType != typeof (DateTime)) { switch (filterObj.Operator) { case FilterOperator.Contains: if (valueType == typeof (string)) whereClause += string.Format(" {0} {1}.Contains(\"{2}\")", filterObj.Conjunction, filterObj.Column, filterObj.Value); break; case FilterOperator.GreaterThan: if (valueType != typeof (string)) whereClause += string.Format(" {0} {1} > {2}", filterObj.Conjunction, filterObj.Column, filterObj.Value); break; case FilterOperator.GreaterThanOrEqual: if (valueType != typeof (string)) whereClause += string.Format(" {0} {1} >= {2}", filterObj.Conjunction, filterObj.Column, filterObj.Value); break; case FilterOperator.LessThan: if (valueType != typeof (string)) whereClause += string.Format(" {0} {1} < {2}", filterObj.Conjunction, filterObj.Column, filterObj.Value); break; case FilterOperator.LessThanOrEqual: if (valueType != typeof (string)) whereClause += string.Format(" {0} {1} <= {2}", filterObj.Conjunction, filterObj.Column, filterObj.Value); break; case FilterOperator.StartsWith: if (valueType != typeof (string)) whereClause += string.Format(" {0} {1}.StartsWith(\"{2}\")", filterObj.Conjunction, filterObj.Column, filterObj.Value); break; case FilterOperator.EndsWith: if (valueType != typeof (string)) whereClause += string.Format(" {0} {1}.EndsWith(\"{2}\")", filterObj.Conjunction, filterObj.Column, filterObj.Value); break; case FilterOperator.Equals: whereClause += string.Format(valueType == typeof (string) ? " {0} {1} == \"{2}\"" : " {0} {1} == {2}", filterObj.Conjunction, filterObj.Column, filterObj.Value); break; case FilterOperator.NotEqual: whereClause += string.Format(valueType == typeof (string) ? " {0} {1} != \"{2}\"" : " {0} {1} != {2}", filterObj.Conjunction, filterObj.Column, filterObj.Value); break; default: throw new ArgumentOutOfRangeException(); } } else { DateTime dt; DateTime.TryParse(filterObj.Value, out dt); switch (filterObj.Operator) { case FilterOperator.Contains: break; case FilterOperator.GreaterThan: whereClause += string.Format(" {0} {1} > DateTime(\"{2}\")", filterObj.Conjunction, filterObj.Column, dt); break; case FilterOperator.GreaterThanOrEqual: whereClause += string.Format(" {0} {1} >= DateTime(\"{2}\")", filterObj.Conjunction, filterObj.Column, dt); break; case FilterOperator.LessThan: whereClause += string.Format(" {0} {1} < DateTime(\"{2}\")", filterObj.Conjunction, filterObj.Column, dt); break; case FilterOperator.LessThanOrEqual: whereClause += string.Format(" {0} {1} <= DateTime(\"{2}\")", filterObj.Conjunction, filterObj.Column, dt); break; case FilterOperator.StartsWith: break; case FilterOperator.EndsWith: break; case FilterOperator.Equals: whereClause += string.Format(" {0} {1} == DateTime(\"{2}\")", filterObj.Conjunction, filterObj.Column, dt); break; case FilterOperator.NotEqual: whereClause += string.Format(" {0} {1} != DateTime(\"{2}\")", filterObj.Conjunction, filterObj.Column, dt); break; default: throw new ArgumentOutOfRangeException(); } } return whereClause; } } 

 public class GridViewModelProvider { internal static CustomersViewModel GetCustomersViewModel(MyDbContext db, PagingInfo PagingData) { int TotalItems = 0; var model = new CustomersViewModel() { Customers = GetResources(db.Customers.AsQueryable(), PagingData, out TotalItems), PagingInfo = new PagingInfo() { CurrentPage = PagingData.CurrentPage, ItemsPerPage = PagingData.ItemsPerPage, PageOptions = new List() { 10, 25, 50, 100 }, ShowPageOptions = true, SearchTerm = PagingData.SearchTerm, Sort = PagingData.Sort, Filters = PagingData.Filters } }; model.PagingInfo.TotalItems = TotalItems; model.JsonPagingInfo = Json.Encode(model.PagingInfo); return model; } private static IQueryable GetResources(IQueryable Customers, PagingInfo PagingData, out int TotalItems) { var customers = Customers; //search if (!string.IsNullOrEmpty(PagingData.SearchTerm)) { customers = customers.Where(x => (x.CompanyName.Contains(PagingData.SearchTerm) || x.ContactTitle.Contains(PagingData.SearchTerm))); } //filter if (PagingData.Filters != null) { foreach (var filterObj in PagingData.Filters) { switch (filterObj.Column) { case "City": if (filterObj.Value.ToLower() != "all") customers = customers.Where(Extensions.GetWhereClause(filterObj, typeof(string))); break; //Add Other Filter Columns Here } } } TotalItems = customers.Count(); //sort customers = customers.OrderBy(x => x.Id); if (PagingData.Sort != null) { switch (PagingData.Sort.Direction) { case SortDirection.Ascending: if (PagingData.Sort.SortColumn == "CompanyName") { customers = customers.OrderBy(x => x.CompanyName); } else if (PagingData.Sort.SortColumn == "ContactTitle") { customers = customers.OrderBy(x => x.ContactTitle); } break; case SortDirection.Descending: if (PagingData.Sort.SortColumn == "CompanyName") { customers = customers.OrderByDescending(x => x.CompanyName); } else if (PagingData.Sort.SortColumn == "ContactTitle") { customers = customers.OrderByDescending(x => x.ContactTitle); } break; case SortDirection.N
                
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