在linq中将字符串转换为int

Question

I have a table tblcatalogue and there is a column classid with datatype varchar.I want a result set containing orderby classid ,but the problem is using order by classid is not giving the desired result.so i tried to convert classid to integer like

var query= itemRepository.GetAll();  
results = query.ToList().OrderBy(x=> Convert.ToInt32(x.ClassId));   

but I am getting sql query like

SELECT 
[Extent1].[Id] AS [Id], 
[Extent1].[SubjectId] AS [SubjectId], 
[Extent1].[SeriesId] AS [SeriesId], 
[Extent1].[Title] AS [Title], 
[Extent1].[Author] AS [Author], 
[Extent1].[ISBN] AS [ISBN], 
[Extent1].[Edition] AS [Edition], 
[Extent1].[Price] AS [Price], 
[Extent1].[Discount] AS [Discount], 
[Extent1].[BoardId] AS [BoardId], 
[Extent1].[ClassId] AS [ClassId]
FROM [dbo].[tblCataLogue] AS [Extent1]
ORDER BY [Extent1].[ClassId] ASC

I wanted converted sql query like

SELECT 
[Extent1].[Id] AS [Id], 
[Extent1].[SubjectId] AS [SubjectId], 
[Extent1].[SeriesId] AS [SeriesId], 
[Extent1].[Title] AS [Title], 
[Extent1].[Author] AS [Author], 
[Extent1].[ISBN] AS [ISBN], 
[Extent1].[Edition] AS [Edition], 
[Extent1].[Price] AS [Price], 
[Extent1].[Discount] AS [Discount], 
[Extent1].[BoardId] AS [BoardId], 
[Extent1].[ClassId] AS [ClassId]
FROM [dbo].[tblCataLogue] AS [Extent1]
ORDER BY covnert(int,[Extent1].[ClassId]) ASC

Because it is giving the right result set

Answer 1

When using ToList() you are executing the query to the database and therefore the ordering you want does not take place. Remove ToList() and the order by clause will also be translated to sql:

results = query.OrderBy(x=> Convert.ToInt32(x.ClassId)).ToList();   

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As for the proceeding error, the Convert.ToInt32 is not supported by the linq provider and cannot be translated to sql. Therefore you should do one of two things:

1. As at the beginning, first retrieve the data to in memory (using ToList() / AsEnumerable() ) and then convert
2. Change the column in the database to be of type int - IMO as your data is a number it should in any case be represented as such..