How do I apply OrderBy on an IQueryable using a st

问题:

public static IQueryable<TResult> ApplySortFilter<T, TResult>(this IQueryable<T> query, string columnName)
  where T : EntityObject
{
  var param = Expression.Parameter(typeof(T), \"o\");
  var body = Expression.PropertyOrField(param,columnName);

  var sortExpression = Expression.Lambda(body, param);
  return query.OrderBy(sortExpression);
}

Because the type for OrderBy is not inferred from sortExpression I need to specify it something like this at run time:

var sortExpression = Expression.Lambda<T, TSortColumn>(body, param);

Or

return query.OrderBy<T, TSortColumn>(sortExpression);

I don\'t think this is possible however as TSortColumn can only be determined during runtime.

Is there a way around this?

回答1:

We did something similar (not 100% the same, but similar) in a LINQ to SQL project. Here\'s the code:

public static IQueryable<T> OrderBy<T>(this IQueryable<T> source, string ordering, params object[] values) {
    var type = typeof(T);
    var property = type.GetProperty(ordering);
    var parameter = Expression.Parameter(type, \"p\");
    var propertyAccess = Expression.MakeMemberAccess(parameter, property);
    var orderByExp = Expression.Lambda(propertyAccess, parameter);
    MethodCallExpression resultExp = Expression.Call(typeof(Queryable), \"OrderBy\", new Type[] { type, property.PropertyType }, source.Expression, Expression.Quote(orderByExp));
    return source.Provider.CreateQuery<T>(resultExp);
}

We didn\'t actually use a generic, we had a known class, but it should work on a generic (I\'ve put the generic placeholder where it should be).

Edit: For descending order, pass in OrderByDescending instead of \"OrderBy\":

MethodCallExpression resultExp = Expression.Call(typeof(Queryable), \"OrderByDescending\", new Type[] { type, property.PropertyType }, source.Expression, Expression.Quote(orderByExp));

回答2:

You can also use Dynamic Linq

Info here http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx

C# download here http://msdn.microsoft.com/en-us/vcsharp/bb894665.aspx

Then just add the using Linq.Dynamic; and you automatically get 2 additional extension methods that can be used like this

return query.OrderBy(\"StringColumnName\");

回答3:

I\'ve extended your functions to add support for Child Properties.

private static LambdaExpression GenerateSelector<TEntity>(String propertyName, out Type resultType) where TEntity : class
{
    // Create a parameter to pass into the Lambda expression (Entity => Entity.OrderByField).
    var parameter = Expression.Parameter(typeof(TEntity), \"Entity\");
    //  create the selector part, but support child properties
    PropertyInfo property;
    Expression propertyAccess;
    if (propertyName.Contains(\'.\'))
    {
            // support to be sorted on child fields.
            String[] childProperties = propertyName.Split(\'.\');
            property = typeof(TEntity).GetProperty(childProperties[0]);
            propertyAccess = Expression.MakeMemberAccess(parameter, property);
            for (int i = 1; i < childProperties.Length; i++)
            {
                    property = property.PropertyType.GetProperty(childProperties[i]);
                    propertyAccess = Expression.MakeMemberAccess(propertyAccess, property);
            }
    }
    else
    {
            property = typeof(TEntity).GetProperty(propertyName);
            propertyAccess = Expression.MakeMemberAccess(parameter, property);
    }
    resultType = property.PropertyType;                     
    // Create the order by expression.
    return Expression.Lambda(propertyAccess, parameter);
}

private static MethodCallExpression GenerateMethodCall<TEntity>(IQueryable<TEntity> source, string methodName, String fieldName) where TEntity : class
{
    Type type = typeof(TEntity);
    Type selectorResultType;
    LambdaExpression selector = GenerateSelector<TEntity>(fieldName, out selectorResultType);
    MethodCallExpression resultExp = Expression.Call(typeof(Queryable), methodName,
                                    new Type[] { type, selectorResultType },
                                    source.Expression, Expression.Quote(selector));
    return resultExp;
}

You can use these functions like:

GenerateMethodCall<TEntity>(source, \"OrderByDescending\", fieldName);

回答4:

I used your idea for extension method for OrderBy. But in case of \"many to many\" I am getting error. For example you have table Site, Customer and Customer_site. For given Site I want to sort by customer name and in OrderBy extension (when I pass \"site.customer\" where customer is navigation property) I get error in line: propertyAccess = Expression.MakeMemberAccess(propertyAccess, property);

This is what I use (with some enhancements :-) ):

public static IQueryable<TEntity> OrderBy<TEntity>(this IQueryable<TEntity> source, string orderByValues) where TEntity : class
{
  IQueryable<TEntity> returnValue = null;

  string orderPair = orderByValues.Trim().Split(\',\')[0];
  string command = orderPair.ToUpper().Contains(\"DESC\") ? \"OrderByDescending\" : \"OrderBy\";

  var type = typeof(TEntity);
  var parameter = Expression.Parameter(type, \"p\");

  string propertyName = (orderPair.Split(\' \')[0]).Trim();

  System.Reflection.PropertyInfo property;
  MemberExpression propertyAccess;

  if (propertyName.Contains(\'.\'))
  {
    // support to be sorted on child fields. 
    String[] childProperties = propertyName.Split(\'.\');
    property = typeof(TEntity).GetProperty(childProperties[0]);
    propertyAccess = Expression.MakeMemberAccess(parameter, property);

    for (int i = 1; i < childProperties.Length; i++)
    {
      Type t = property.PropertyType;
      if (!t.IsGenericType)
      {
        property = t.GetProperty(childProperties[i]);
      }
      else
      {
        property = t.GetGenericArguments().First().GetProperty(childProperties[i]);
      }

      propertyAccess = Expression.MakeMemberAccess(propertyAccess, property);
    }
  }
  else
  {
    property = type.GetProperty(propertyName);
    propertyAccess = Expression.MakeMemberAccess(parameter, property);
  }

  var orderByExpression = Expression.Lambda(propertyAccess, parameter);

  var resultExpression = Expression.Call(typeof(Queryable), command, new Type[] { type, property.PropertyType },

  source.Expression, Expression.Quote(orderByExpression));

  returnValue = source.Provider.CreateQuery<TEntity>(resultExpression);

  if (orderByValues.Trim().Split(\',\').Count() > 1)
  {
    // remove first item
    string newSearchForWords = orderByValues.ToString().Remove(0, orderByValues.ToString().IndexOf(\',\') + 1);
    return source.OrderBy(newSearchForWords);
  }

  return returnValue;
}

Regards

Slobodan

回答5:

It seems that this is the way to do it, now to verify that:

// ***** OrderBy(company => company) *****
// Create an expression tree that represents the expression
// \'whereCallExpression.OrderBy(company => company)\'
MethodCallExpression orderByCallExpression = Expression.Call(
    typeof(Queryable),
    \"OrderBy\",
    new Type[] { queryableData.ElementType, queryableData.ElementType },
    whereCallExpression,
    Expression.Lambda<Func<string, string>>(pe, new ParameterExpression[] { pe }));
// ***** End OrderBy *****

回答6:

If you are able to add \"System.Linq.Dynamic\" package then, Too easy without any complication,

fisrt insatll package \"System.Linq.Dynamic\" from NuGet package manager then try as below as your need,

Ex:

public IQueryable<TEntity> GetWithInclude(Expression<Func<TEntity, bool>> predicate,
                    List<string> sortBy, int pageNo, int pageSize = 12, params string[] include)
        {
            try
            {
                var numberOfRecordsToSkip = pageNo * pageSize;
                var dynamic = DbSet.AsQueryable();

                foreach (var s in include)
                {
                    dynamic.Include(s);
                }
                 return dynamic.OrderBy(\"CreatedDate\").Skip(numberOfRecordsToSkip).Take(pageSize);


            }
            catch (Exception e)
            {
                throw new Exception(e.Message);
            }
        }

Hope this will help

回答7:

I fixed this code a bit: https://stackoverflow.com/a/1670085/5852630

This code works with sequential sorting: first execute \"OrderBy\", then \"ThenBy\"(Not \"OrderBy\"!)

public static IQueryable<TEntity> OrderBy<TEntity>(this IQueryable<TEntity> source, string orderByValues) where TEntity : class
{
    IQueryable<TEntity> returnValue = null;

    string[] orderPairs = orderByValues.Trim().Split(\',\');

    Expression resultExpression = source.Expression;

    string strAsc = \"OrderBy\";
    string strDesc = \"OrderByDescending\";

    foreach (string orderPair in orderPairs)
    {
        if (string.IsNullOrWhiteSpace(orderPair))
            continue;

        string[] orderPairArr = orderPair.Trim().Split(\' \');

        string propertyName = orderPairArr[0].Trim();
        string orderNarrow = orderPairArr.Length > 1 ? orderPairArr[1].Trim() : string.Empty;

        string command = orderNarrow.ToUpper().Contains(\"DESC\") ? strDesc : strAsc;

        Type type = typeof(TEntity);
        ParameterExpression parameter = Expression.Parameter(type, \"p\");

        System.Reflection.PropertyInfo property;
        Expression propertyAccess;

        if (propertyName.Contains(\'.\'))
        {
            // support to be sorted on child fields. 
            String[] childProperties = propertyName.Split(\'.\');
            property = typeof(TEntity).GetProperty(childProperties[0]);
            propertyAccess = Expression.MakeMemberAccess(parameter, property);

            for (int i = 1; i < childProperties.Length; i++)
            {
                Type t = property.PropertyType;
                if (!t.IsGenericType)
                {
                    property = t.GetProperty(childProperties[i]);
                }
                else
                {
                    property = t.GetGenericArguments().First().GetProperty(childProperties[i]);
                }

                propertyAccess = Expression.MakeMemberAccess(propertyAccess, property);
            }
        }
        else
        {
            property = type.GetProperty(propertyName);
            propertyAccess = Expression.MakeMemberAccess(parameter, property);
        }

        if (property.PropertyType == typeof(object))
        {
            propertyAccess = Expression.Call(propertyAccess, \"ToString\", null);
        }

        LambdaExpression orderByExpression = Expression.Lambda(propertyAccess, parameter);

        resultExpression = Expression.Call(typeof(Queryable), command, new Type[] { type, property.PropertyType == typeof(object) ? typeof(string) : property.PropertyType },
            resultExpression, Expression.Quote(orderByExpression));

        strAsc = \"ThenBy\";
        strDesc = \"ThenByDescending\";
    }

    returnValue = source.Provider.CreateQuery<TEntity>(resultExpression);

    return returnValue;
}

回答8:

Here is my adaptation from @Davy Landman\'s answer (I wanted an extension method) and I simplified a bit.

public static IQueryable<T> SortBy<T>(this IQueryable<T> source, 
                                      String propertyName, 
                                      WebControls.SortDirection direction)
    {
        if (source == null) throw new ArgumentNullException(\"source\");
        if (String.IsNullOrEmpty(propertyName)) return source;

        // Create a parameter to pass into the Lambda expression
        //(Entity => Entity.OrderByField).
        var parameter = Expression.Parameter(typeof(T), \"Entity\");

        //  create the selector part, but support child properties (it works without . too)
        String[] childProperties = propertyName.Split(\'.\');
        MemberExpression property = Expression.Property(parameter, childProperties[0]);
        for (int i = 1; i < childProperties.Length; i++)
        {
            property = Expression.Property(property, childProperties[i]);
        }

        LambdaExpression selector = Expression.Lambda(property, parameter);

        string methodName = (direction > 0) ? \"OrderByDescending\" : \"OrderBy\";

        MethodCallExpression resultExp = Expression.Call(typeof(Queryable), methodName,
                                        new Type[] { source.ElementType, property.Type },
                                        source.Expression, Expression.Quote(selector));

        return source.Provider.CreateQuery<T>(resultExp);
    }

It can be used like this:

gridview1.DataSource = DbContext.TB_CARS.SortBy(\"model\", SortDirection.Descending);
//OR
gridview1.DataSource = DbContext.TB_CARS.SortBy(\"owner.first_name\", 0);