Question

public ActionResult Load()
        {
            string search = Request.Form.GetValues("search[value]")[0];

            var draw = Request.Form.GetValues("draw").FirstOrDefault();
            var start = Request.Form.GetValues("start").FirstOrDefault();
            var length = Request.Form.GetValues("length").FirstOrDefault();

            var sortColumn = Request.Form.GetValues("columns[" +
                Request.Form.GetValues("order[0][column]").FirstOrDefault() + "][name]").FirstOrDefault();
            var sortColumnDir = Request.Form.GetValues("order[0][dir]").FirstOrDefault();

            int pageSize = length != null ? Convert.ToInt32(length) : 0;
            int skip = start != null ? Convert.ToInt32(start) : 0;
            int totalRecords = 0;


            var v = (from a in DataContext.Company select a);

            //Search
            if (!string.IsNullOrEmpty(search) &&
            !string.IsNullOrWhiteSpace(search))
            {
                v.Where(x => x.Name == search);
            }

            //Ordinamento
            if (!(string.IsNullOrEmpty(sortColumn) && string.IsNullOrEmpty(sortColumnDir)))
                v = v.OrderBy(sortColumn + " " + sortColumnDir);

            totalRecords = v.Count();
            var data = v.Skip(skip).Take(pageSize).ToList();

            return Json(new
            {
                draw = draw,
                recordsFiltered = totalRecords,
                recordsTotal = totalRecords,
                data = data
            }, JsonRequestBehavior.AllowGet);
        }

实际上，我正在使用Jquery Datatable和服务器端模式，这种方法运行得很好，但我想用它来做法。通过这种方式，我可以重用我的方法。第一个问题是在“搜索”部分，因为我不知道如何动态传递数据库表（datacontext）。现在通过“var v”，但我通过表“公司”所以它是静态的（我需要将表作为参数传递。

无论如何，如果我解决它，我需要将lamba表达式作为参数传递，因为我想搜索特定的表列。

然而，我的问题的真正问题是：如何使这个函数动态化，以便我可以使用它而不重复代码？

谢谢

Answer 1

你传递给你的功能两个功能。第一个Func＆gt;获取DbContext并返回选定的集合。

第二个是过滤函数，它接受一个元素并对其进行过滤。

这会改变这一行：

v.Where(x => x.Name == search);

修改

您的功能签名将如下所示：

public IEnumerable<T> Search(IQueryable<T> entites, Func<T,bool> filter) { // your code here }

Answer 2

我尝试为Jquery DataTable创建一个小的查询构建器。可能会有错误，但这将是一个良好的开端。这可能会对你有所帮助。

我将此useful answer用作模型绑定的参考。我不在这里编写代码，不重复它。

使阅读请求参数的过程标准化
```
public ActionResult Load(DTParameterModel dtParameters)
{
    // do some thing
}
```
Jquery DataTable的查询构建器。
- 搜索多列
- 按多列排序
- 寻呼

JqueryDataTableQueryBuilder.cs

public class JqueryDataTableQueryBuilder
{
    private static readonly MethodInfo OrderByMethod = typeof(Queryable)
        .GetMethods().
        Single(method => method.Name == "OrderBy"
            && method.GetParameters().Length == 2);

    private static readonly MethodInfo OrderByDescendingMethod = typeof(Queryable)
        .GetMethods().Single(method => method.Name == "OrderByDescending"
            && method.GetParameters().Length == 2);

    public static IQueryable<T> BuildQuery<T>(IQueryable<T> query, DTParameterModel dtParameters)
    {
        IQueryable<T> q = query;
        //I skiped regex search
        var searchColumns = dtParameters.Columns.Where(c => c.Searchable).Select(c => c.Name).ToArray();
        if (searchColumns.Length > 0)
            if (!string.IsNullOrEmpty(dtParameters.Search.Value) && !string.IsNullOrWhiteSpace(dtParameters.Search.Value))
            {
                int i = 0;
                var par = Expression.Parameter(typeof(T), "x");
                Expression exp = Expression.Constant(false);
                //we need to bind search expressions with 'OR'
                while (i < searchColumns.Length)
                {
                    var expNext = GetSearchExpression<T>(searchColumns[i], dtParameters.Search.Value,par);
                    var expInvoke = Expression.Invoke(expNext, par);
                    exp = Expression.OrElse(exp, expNext.Body);
                    i++;
                }
                var ex = Expression.Lambda<Func<T, bool>>(exp,par);
                q = q.Where(ex);
            }
        // order by 
        DTColumn[] columns = dtParameters.Columns.ToArray();
        foreach (var order in dtParameters.Order)
        {
            var orderColumn = columns[order.Column].Name;
            var dir = order.Dir;
            q = OrderByQuery(q, orderColumn, dir);
        }
        return q;
    }

    public static object GetDTResult<T>(DTParameterModel dtParameters, IQueryable<T> query,Expression<Func<T,object>> func = null)
    {
        var totalRecords = query.Count();
        query = query.Skip(dtParameters.Start).Take(dtParameters.Length);
        object data = func == null ? (object) query.ToArray() : query.Select(func).ToArray();
        var result = new
        {
            draw = dtParameters.Draw,
            recordsFiltered = totalRecords,
            recordsTotal = totalRecords,
            data = data
        };
        return result;
    }

    static Expression<Func<T, bool>> GetSearchExpression<T>(string propertyName, string propertyValue,ParameterExpression p)
    {
        var propertyExp = Expression.Property(p, propertyName);
        // we need to call string.Contains method
        MethodInfo method = typeof(string).GetMethod("Contains", new[] { typeof(string) });
        var valueExp = Expression.Constant(propertyValue, typeof(string));
        var containsMethodExp = Expression.Call(propertyExp, method, valueExp);
        return Expression.Lambda<Func<T, bool>>(containsMethodExp, p);
    }
    static IQueryable<T> OrderByQuery<T>(IQueryable<T> source, string propertyName, string dir)
    {
        IQueryable<T> query = source;
        Type entityType = typeof(T);
        if (entityType.GetProperty(propertyName, BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.Instance) == null)
            throw new NullReferenceException("order by " + propertyName);
        ParameterExpression paramterExpression = Expression.Parameter(entityType);
        Expression orderByProperty = Expression.Property(paramterExpression, propertyName);
        LambdaExpression lambda = Expression.Lambda(orderByProperty, paramterExpression);
        MethodInfo genericMethod = !string.IsNullOrEmpty(dir) && !string.IsNullOrWhiteSpace(dir) && dir.ToUpper().Equals("DESC")
            ? OrderByDescendingMethod.MakeGenericMethod(entityType, orderByProperty.Type)
            : OrderByMethod.MakeGenericMethod(entityType, orderByProperty.Type);
        object ret = genericMethod.Invoke(null, new object[] { query, lambda });
        return (IQueryable<T>)ret;
    }
}

是：

实体模型：

public partial class Customer { public int Id { get; set; } public string Name { get; set; } public string LastName { get; set; } public DateTime CreatedDate { get; set; } }

<强>标记：

<script type="text/javascript"> $(function () { $('#example').DataTable({ "processing": true, "serverSide": true, "ajax": "/JqTableTest/Load" }); }); </script> <table id="example" class="display" cellspacing="0" width="100%"> <thead> <tr> <th data-orderable="true" data-searchable="false" data-name="Id" data-data="Id">Id</th> <th data-orderable="true" data-searchable="true" data-name="Name" data-data="Name">First name</th> <th data-orderable="true" data-searchable="true" data-name="LastName" data-data="LastName"> Last name</th> </tr> </thead> </table>

<强> CONTROLER：

public ActionResult Load(DTParameterModel dtParameters) { using (Data.Entities context = new Data.Entities()) { var query = context.Customer.AsQueryable(); query = JqueryDataTableQueryBuilder.BuildQuery(query, dtParameters); var result = JqueryDataTableQueryBuilder.GetDTResult(dtParameters, query); return Json(result, JsonRequestBehavior.AllowGet); } }

查询：

-- count SELECT [GroupBy1].[A1] AS [C1] FROM ( SELECT COUNT(1) AS [A1] FROM [dbo].[Customer] AS [Extent1] ) AS [GroupBy1] -- result SELECT TOP (10) [Extent1].[Id] AS [Id], [Extent1].[Name] AS [Name], [Extent1].[LastName] AS [LastName], [Extent1].[CreatedDate] AS [CreatedDate] FROM ( SELECT [Extent1].[Id] AS [Id], [Extent1].[Name] AS [Name], [Extent1].[LastName] AS [LastName], [Extent1].[CreatedDate] AS [CreatedDate], row_number() OVER (ORDER BY [Extent1].[Id] ASC) AS [row_number] FROM [dbo].[Customer] AS [Extent1] ) AS [Extent1] WHERE [Extent1].[row_number] > 0 ORDER BY [Extent1].[Id] ASC

您可以指定结果列

public ActionResult Load(DTParameterModel dtParameters) { using (Data.Entities context = new Data.Entities()) { var query = context.Customer.AsQueryable(); query = JqueryDataTableQueryBuilder.BuildQuery(query, dtParameters); var result = JqueryDataTableQueryBuilder.GetDTResult(dtParameters, query, a => new { a.Id, a.Name, a.LastName }); return Json(result, JsonRequestBehavior.AllowGet); } }

查询：

SELECT TOP (10) [Extent1].[Id] AS [Id], [Extent1].[Name] AS [Name], [Extent1].[LastName] AS [LastName] FROM ( SELECT [Extent1].[Id] AS [Id], [Extent1].[Name] AS [Name], [Extent1].[LastName] AS [LastName], row_number() OVER (ORDER BY [Extent1].[Id] ASC) AS [row_number] FROM [dbo].[Customer] AS [Extent1] ) AS [Extent1] WHERE [Extent1].[row_number] > 0 ORDER BY [Extent1].[Id] ASC

请求搜索参数：

draw:6 columns[0][data]:Id columns[0][name]:Id columns[0][searchable]:false columns[0][orderable]:true columns[0][search][value]: columns[0][search][regex]:false columns[1][data]:Name columns[1][name]:Name columns[1][searchable]:true columns[1][orderable]:true columns[1][search][value]: columns[1][search][regex]:false columns[2][data]:LastName columns[2][name]:LastName columns[2][searchable]:true columns[2][orderable]:true columns[2][search][value]: columns[2][search][regex]:false order[0][column]:0 order[0][dir]:asc start:0 length:10 search[value]:abc search[regex]:false

查询：

SELECT TOP (10) [Filter1].[Id] AS [Id], [Filter1].[Name] AS [Name], [Filter1].[LastName] AS [LastName] FROM ( SELECT [Extent1].[Id] AS [Id], [Extent1].[Name] AS [Name], [Extent1].[LastName] AS [LastName], row_number() OVER (ORDER BY [Extent1].[Id] ASC) AS [row_number] FROM [dbo].[Customer] AS [Extent1] WHERE ([Extent1].[Name] LIKE N'%abc%') OR ([Extent1].[LastName] LIKE N'%abc%') ) AS [Filter1] WHERE [Filter1].[row_number] > 0 ORDER BY [Filter1].[Id] ASC

Lamba作为参数C＃MVC LINQ

2 个答案: