方法：

///

 

<summary>

///

 扩展Linqstring字段排序

///

 

</summary>

public 

static 

class StringFieldSorting

{

    

#region Private expression tree helpers

    

private 

static LambdaExpression GenerateSelector<TEntity>(String propertyName, 

out Type resultType) 

where TEntity : 

class

    {

        PropertyInfo property;

        Expression propertyAccess;

        

var parameter = Expression.Parameter(

typeof(TEntity), 

"

Entity

");

            

        

if (propertyName.Contains(

'

.

'))

        {

            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;

        

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;

    }

    

#endregion

    

public 

static IOrderedQueryable<TEntity> OrderBy<TEntity>(

this IQueryable<TEntity> source, 

string fieldName) 

where TEntity : 

class

    {

        MethodCallExpression resultExp = GenerateMethodCall<TEntity>(source, 

"

OrderBy

", fieldName);

        

return source.Provider.CreateQuery<TEntity>(resultExp) 

as IOrderedQueryable<TEntity>;

    }

    

public 

static IOrderedQueryable<TEntity> OrderByDescending<TEntity>(

this IQueryable<TEntity> source, 

string fieldName) 

where TEntity : 

class

    {

        MethodCallExpression resultExp = GenerateMethodCall<TEntity>(source, 

"

OrderByDescending

", fieldName);

        

return source.Provider.CreateQuery<TEntity>(resultExp) 

as IOrderedQueryable<TEntity>;

    }

    

public 

static IOrderedQueryable<TEntity> ThenBy<TEntity>(

this IOrderedQueryable<TEntity> source, 

string fieldName) 

where TEntity : 

class

    {

        MethodCallExpression resultExp = GenerateMethodCall<TEntity>(source, 

"

ThenBy

", fieldName);

        

return source.Provider.CreateQuery<TEntity>(resultExp) 

as IOrderedQueryable<TEntity>;

    }

    

public 

static IOrderedQueryable<TEntity> ThenByDescending<TEntity>(

this IOrderedQueryable<TEntity> source, 

string fieldName) 

where TEntity : 

class

    {

        MethodCallExpression resultExp = GenerateMethodCall<TEntity>(source, 

"

ThenByDescending

", fieldName);

        

return source.Provider.CreateQuery<TEntity>(resultExp) 

as IOrderedQueryable<TEntity>;

    }

    

public 

static IOrderedQueryable<TEntity> OrderUsingSortExpression<TEntity>(

this IQueryable<TEntity> source, 

string sortExpression) 

where TEntity : 

class

    {

        String[] orderFields = sortExpression.Split(

'

,

');

        IOrderedQueryable<TEntity> result = 

null;

        

for (

int currentFieldIndex = 

0; currentFieldIndex < orderFields.Length; currentFieldIndex++)

        {

            String[] expressionPart = orderFields[currentFieldIndex].Trim().Split(

'

 

');

            String sortField = expressionPart[

0];

            Boolean sortDescending = (expressionPart.Length == 

2) && (expressionPart[

1].Equals(

"

DESC

", StringComparison.OrdinalIgnoreCase));

            

if (sortDescending)

            {

                result = currentFieldIndex == 

0 ? source.OrderByDescending(sortField) : result.ThenByDescending(sortField);

            }

            

else

            {

                result = currentFieldIndex == 

0 ? source.OrderBy(sortField) : result.ThenBy(sortField);

            }

        }

        

return result;

    }

}

调用：

var query = (

from d 

in ((VinnoTech.Gaia2.DB.g2_dsource[])result)

            join p 

in WebApiApplication.entities.g2_propnames

            on d.dsource_item equals p.prop_name

            

orderby sidx

            

select 

new

            {

                d.dsource_id,

                d.dsource_name,

                dsource_item = p.prop_description,

                d.dsource_description,

                dsource_status = d.dsource_status == 

"

1

" ? 

"

启用

" : 

"

禁用

",

                d.dsource_expiredday,

                dsource_alarmhigh = (d.dsource_alarmhigh == -

65535 || d.dsource_alarmhigh == 

65535) ? 

"

未禁用

" : d.dsource_alarmhigh.ToString(),

                dsource_alarmlow = (d.dsource_alarmlow == -

65535 || d.dsource_alarmhigh == 

65535) ? 

"

未禁用

" : d.dsource_alarmhigh.ToString(),

                dsource_alarmdeltadata = (d.dsource_alarmdeltadata == -

65535 || d.dsource_alarmhigh == 

65535) ? 

"

未禁用

" : d.dsource_alarmhigh.ToString(),

                dsource_alarmidle = (d.dsource_alarmidle == -

65535 || d.dsource_alarmhigh == 

65535) ? 

"

未禁用

" : d.dsource_alarmhigh.ToString(),

                d.dsource_formula,

                dsource_updatetime = d.dsource_updatetime.ToString(

"

yyyy-MM-dd HH:mm:ss

")

            }).AsQueryable();

            

page = page <= query.Count() / rows + 

1 ? page : 

1;

query = query.OrderUsingSortExpression(

"

dsource_name asc,dsource_item desc

").Skip(rows * (page - 

1)).Take(rows);