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c# – 参数“d”未绑定在指定的LINQ to Entities查询表达式中

分类：C#作者：编程之家
这是什么错误：

The parameter ‘d’ was not bound in the specified LINQ to Entities
query expression

查看详细信息 ：

private static IEnumerable<T> ConnectToDatabase(IQueryable dbSet,ParameterExpression pe,IEnumerable<Expression> expressions,string orderby,bool desc)
{
  // expressions = 
    Expression body = null;
    if (expressions.Any())
    {
        foreach (Expression expression in expressions)
        {
            body = ExpressionExtensions.JoinExpressions(body == null,Expression.Or,body,expression);
        }
    }
    if (body == null)
    {
        Expression left = Expression.Property(pe,"ID");
        Expression right = Expression.Constant(-1);
        body = Expression.NotEqual(left,right);
    }
    IQueryable<T> results;
    MethodCallExpression whereCallExpression = Expression.Call(
        typeof(Queryable),"Where",new[] { dbSet.ElementType },dbSet.Expression,Expression.Lambda<Func<T,bool>>(body,new[] { pe }));

    var ModelType = typeof(T);
    pe = Expression.Parameter(ModelType,"x");
    var propertyInfoOrderBy = GetPropertyInfo(orderby);
    var propertyAccess = Expression.MakeMemberAccess(pe,propertyInfoOrderBy);
    var orderByExp = Expression.Lambda(propertyAccess,pe);

    MethodCallExpression orderByCallExpression = Expression.Call(
        typeof(Queryable),"OrderBy",new[] { ModelType,propertyInfoOrderBy.PropertyType },whereCallExpression,Expression.Quote(orderByExp));

    if (desc)
    {
        MethodCallExpression resultExp = Expression.Call(
            typeof(Queryable),"OrderByDescending",orderByCallExpression,Expression.Quote(orderByExp));

        results = dbSet.Provider.createquery<T>(resultExp);
    }
    else
    {
        results = dbSet.Provider.createquery<T>(orderByCallExpression);
    }
    return results.ToList();
}

表达式：

身体 ：

whereCallExpression：

orderByCallExpression：

错误：

JN_News课程：

public class JN_News
{
    public int ID { get; set; }
    public string Title { get; set; }
    public string Description { get; set; }
    public string NewsLink { get; set; }
    public DateTime PubDate { get; set; }
    public string ImageLink { get; set; }
    public bool Isdisplay { get; set; }
    public Decimal? Rate { get; set; }
    public int Newscategories_ID { get; set; }
    public virtual JN_Newscategories JN_Newscategories { get; set; }
}

JN_Newscategories类：

public class JN_Newscategories
{
    public int ID { get; set; }
    public string NewscategoriesFa { get; set; }
    public string NewscategoriesEn { get; set; }
    public bool IsGetNews { get; set; }
    public virtual ICollection<JN_News> JN_News { get; set; }

    public JN_Newscategories()
    {
        JN_News = new Collection<JN_News>();
    }
}

更新：

当我消除了以下两个陈述时.好好工作：

我的所有代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using System.Reflection;

namespace NewsSiteApk.Data.DynamicSearchLibrary
{
    public static class SearchUsingExpression<T> where T : class
    {
        public static IEnumerable<T> Search(IEnumerable<T> listofT,string search,string orderBy,bool desc,int pageIndex,int pageSize)
        {
            listofT = GetlistofData(listofT,search,orderBy,desc).Skip((pageIndex - 1) * pageSize).Take(pageSize);
            return listofT;
        }
        public static int GetCount(IEnumerable<T> listofT,string search)
        {
            listofT = GetlistofData(listofT,"id",true);
            return listofT.Count();
        }

        private static IEnumerable<T> GetlistofData(IEnumerable<T> listofT,bool desc)
        {
            var modelType = typeof(T);
            ParameterExpression pe = Expression.Parameter(modelType,"d");
            var expressions = new List<Expression>();
            if (!string.IsNullOrEmpty(search))
            {
                expressions.AddRange(GetExpressions(modelType.Name,pe));
            }
            var connectToDatabase = ConnectToDatabase(listofT.AsQueryable(),pe,expressions,desc);
            return connectToDatabase;
        }


        private static IEnumerable<T> ConnectToDatabase(IQueryable dbSet,bool desc)
        {
            Expression body = null;
            if (expressions.Any())
            {
                foreach (Expression expression in expressions)
                {
                    body = ExpressionExtensions.JoinExpressions(body == null,expression);
                }
            }
            if (body == null)
            {
                Expression left = Expression.Property(pe,"ID");
                Expression right = Expression.Constant(-1);
                body = Expression.NotEqual(left,right);
            }
            IQueryable<T> results;
            MethodCallExpression whereCallExpression = Expression.Call(
                typeof(Queryable),new[] { pe }));

            var propertyInfoOrderBy = GetPropertyInfo(orderby);
            var propertyAccess = Expression.MakeMemberAccess(pe,propertyInfoOrderBy);
            var orderByExp = Expression.Lambda(propertyAccess,pe);

            var ModelType = typeof(T);
            MethodCallExpression orderByCallExpression = Expression.Call(
                typeof(Queryable),Expression.Quote(orderByExp));

            if (desc)
            {
                MethodCallExpression resultExp = Expression.Call(
                    typeof(Queryable),Expression.Quote(orderByExp));

                results = dbSet.Provider.createquery<T>(resultExp);
            }
            else
            {
                results = dbSet.Provider.createquery<T>(orderByCallExpression);
            }
            return results.ToList();
        }

        private static IEnumerable<Expression> GetExpressions(string modelName,ParameterExpression pe)
        {
            var expressions = new List<Expression>();
            var fieldModels = GetFields(modelName);

            foreach (FieldModel fieldModel in fieldModels)
            {
                IEnumerable<Expression> conditionsWithSubModel;
                if (fieldModel.NameEn.Contains("[]"))
                {
                    conditionsWithSubModel = GetConditionsWithSubModelList(search,fieldModel.NameEn,pe);
                }
                else if (fieldModel.NameEn.Contains("."))
                {
                    conditionsWithSubModel = GetConditionsWithSubModel(search,fieldModel.NameEn);
                }
                else
                {
                    conditionsWithSubModel = GetConditionsWithoutSubModel(search,fieldModel.NameEn);
                }
                if (conditionsWithSubModel != null)
                    expressions.AddRange(conditionsWithSubModel);
            }
            return expressions;
        }


        private static IEnumerable<Expression> GetConditionsWithoutSubModel(string search,string parametr)
        {
            var expressions = new List<Expression>();

            foreach (var splitSeacrh in search.Split(' '))
            {
                Expression left = Expression.Property(pe,parametr);
                Expression right = Expression.Constant(splitSeacrh);
                MethodCallExpression conditionExpression = Expression.Call(left,typeof(string).getmethod("Contains"),right);
                expressions.Add(conditionExpression);
            }

            return expressions;
        }
        private static IEnumerable<Expression> GetConditionsWithSubModel(string search,string parameter)
        {
            //         output.Where(d => d.JN_Newscategories.NewscategoriesEn.Contains(""));
            var expressions = new List<Expression>();
            var strings = parameter.Split('$');
            var modelName = strings[0]; // Like : JN_News
            var subModelName = strings[1].Split('.')[0];// Like : JN_Newscategories
            var subModelField = strings[1].Split('.')[1];// Like : NewscategoriesEn

            foreach (var splitSeacrh in search.Split(' '))
            {
                Type modelClass = GetModel(modelName);
                Type submodelClass = GetModel(subModelName);
                ParameterExpression peSubModel = Expression.Parameter(modelClass,"d");
                Expression leftSubModel = Expression.Property(peSubModel,modelClass.GetProperty(subModelName));
                Expression ex = Expression.Property(leftSubModel,submodelClass.GetProperty(subModelField));
                Expression rightSubModel = Expression.Constant(splitSeacrh);
                MethodCallExpression conditionExpressionSubModel = Expression.Call(ex,rightSubModel);

                expressions.Add(conditionExpressionSubModel);
            }

            return expressions;
        }

        private static IEnumerable<Expression> GetConditionsWithSubModelList(string search,string parameter,ParameterExpression peModel)
        {
            parameter = parameter.Replace("[]",string.Empty);

            var expressions = new List<Expression>();
            var subModelName = parameter.Split('.')[0];
            var subModelField = parameter.Split('.')[1];
            foreach (var splitSeacrh in search.Split(' '))
            {
                Type modelClass = GetModel(subModelName);
                var subModelProperty = GetPropertyInfo(subModelName);
                ParameterExpression peSubModel = Expression.Parameter(modelClass,modelClass.GetProperty(subModelField));
                Expression rightSubModel = Expression.Constant(splitSeacrh);
                MethodCallExpression conditionExpressionSubModel = Expression.Call(leftSubModel,rightSubModel);
                LambdaExpression anyLambdaSubModelForModel = Expression.Lambda(conditionExpressionSubModel,peSubModel);
                MethodInfo anyMethodForModel = CreateAnyMethodGeneric(subModelProperty);
                Expression lambedaSubModelForExpressionModel = Expression.Property(peModel,subModelProperty);
                Expression expression = Expression.Call(anyMethodForModel,lambedaSubModelForExpressionModel,anyLambdaSubModelForModel);
                expressions.Add(expression);
            }

            return expressions;
        }

        private static Type GetModel(string name)
        {
            return (typeof(T).Assembly).GetTypes()
                .First(d => string.Equals(d.Name,name,StringComparison.CurrentCultureIgnoreCase));
        }

        private static PropertyInfo GetPropertyInfo(string name)
        {
            return typeof(T).GetProperties().First(d => string.Equals(d.Name,StringComparison.CurrentCultureIgnoreCase));
        }

        private static MethodInfo CreateAnyMethodGeneric(PropertyInfo propYekiBeAkhar,string methodName = "Any")
        {
            return
                typeof(Enumerable).getmethods()
                    .Single(m => m.Name == methodName && m.GetParameters().Length == 2)
                    .MakeGenericmethod(propYekiBeAkhar.PropertyType.GenericTypeArguments[0]);
        }

        private static IEnumerable<FieldModel> GetFields(string modelName)
        {
            var fieldsFactory = new FieldsFactory();
            var fieldModels = fieldsFactory.GetClause(modelName);
            return fieldModels;
        }
    }
}

野外工厂类：

public class FieldsFactory
    {
        public List<FieldModel> GetClause(string modelName)
        {
            var type = typeof(FieldsFactory);
            var methodInfos = type.getmethod("Get" + modelName + "Fields",BindingFlags.NonPublic | BindingFlags.Instance);
            var listofFields = (List<FieldModel>)methodInfos.Invoke(this,null);
            return listofFields;
        }

        private List<FieldModel> GetJN_NewscategoriesFields()
        {
            var fields = new List<FieldModel>
            {
                new FieldModel
                {
                    NameEn = "NewscategoriesFa",},new FieldModel
                {
                    NameEn = "NewscategoriesEn",new FieldModel
                {
                    NameEn = "JN_News[].Title",new FieldModel
                {
                    NameEn = "JN_News[].Description",}
            };
            return fields;
        }
        private List<FieldModel> GetJN_NewsFields()
        {
            var fields = new List<FieldModel>
            {
                new FieldModel
                {
                    NameEn = "Title",new FieldModel
                {
                    NameEn = "JN_News$JN_Newscategories.NewscategoriesFa",new FieldModel
                {
                    NameEn = "JN_News$JN_Newscategories.NewscategoriesEn",}
            };
            return fields;
        }
    }

解决方法

我fooooooooooound.我很开心.

只是,我替换了以下方法：

private static IEnumerable<Expression> GetConditionsWithSubModel(string search,string parameter)
{
    //         output.Where(d => d.JN_Newscategories.NewscategoriesEn.Contains(""));
    var expressions = new List<Expression>();
    var strings = parameter.Split('$');
    var modelName = strings[0];
    var subModelName = strings[1].Split('.')[0];
    var subModelField = strings[1].Split('.')[1];

    foreach (var splitSeacrh in search.Split(' '))
    {
        Type modelClass = GetModel(modelName);
        Type submodelClass = GetModel(subModelName);
        ParameterExpression peSubModel = Expression.Parameter(modelClass,"d");
        Expression leftSubModel = Expression.Property(peSubModel,modelClass.GetProperty(subModelName));
        Expression ex = Expression.Property(leftSubModel,submodelClass.GetProperty(subModelField));
        Expression rightSubModel = Expression.Constant(splitSeacrh);
        MethodCallExpression conditionExpressionSubModel = Expression.Call(ex,rightSubModel);

        expressions.Add(conditionExpressionSubModel);
    }

    return expressions;
}

使用以下方法：

private static IEnumerable<Expression> GetConditionsWithSubModel(string search,string parameter)
{
    //         output.Where(d => d.JN_Newscategories.NewscategoriesEn.Contains(""));
    var expressions = new List<Expression>();
    var strings = parameter.Split('$');
    var modelName = strings[0];
    var subModelName = strings[1].Split('.')[0];
    var subModelField = strings[1].Split('.')[1];

    foreach (var splitSeacrh in search.Split(' '))
    {
        Type modelClass = GetModel(modelName);
        Type submodelClass = GetModel(subModelName);
        Expression leftSubModel = Expression.Property(pe,rightSubModel);

        expressions.Add(conditionExpressionSubModel);
    }

    return expressions;
}

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