How to get Column name and corresponding Database

问题:

Suppose I have this table:

How can I get the column name and database datatype from DbContext in Entity Framework Core?

Tips

1. The column with name clg# converted to clg1 by EF Core Scaffold tool so I need real column name not current EF name

2. I need database type, not clrType, of course the must be cross platform. Maybe I will change the database so the method must work too.

Desired result:

    <D.clg#, int>
    <D.clgname, nvarchar(50)>
    <D.city, nvarchar(50)>
    <D.pname, nvarchar(50)>

Can anyone provide a solution ?

回答1:

Update: Starting with EF Core 2.0, the things have changed, so the original answer does not apply anymore. Now EF Core builds separate model for each database type, so the code is much simpler and uses directly the Relational() extensions:

var entityType = dbContext.Model.FindEntityType(clrEntityType);

// Table info 
var tableName = entityType.Relational().TableName;
var tableSchema = entityType.Relational().Schema;

// Column info 
foreach (var property in entityType.GetProperties())
{
    var columnName = property.Relational().ColumnName;
    var columnType = property.Relational().ColumnType;
};

Original answer (EF Core 1.x):

Getting the access to the associated metadata is much easier in EF Core compared to EF - you start from DbContext.Model property to get IModel, use GetEntityTypes or FindEntityType to get IEntityType, then GetProperties or FindProperty to get IProperty etc.

However the problem is that EF Core allows you to use different setting fro different target database. In order to get the attributes corresponding to the current database used by the context, you need to get access to the IRelationalDatabaseProviderServices and use AnnotationProvider and TypeMapper properties to get the information needed.

Here is an example:

using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Infrastructure;
using Microsoft.EntityFrameworkCore.Internal;
using Microsoft.EntityFrameworkCore.Storage;

public class DbColumnInfo
{
    public string Name;
    public string Type;
}

public static class RelationalDbHelpers
{
    public static IEnumerable<DbColumnInfo> GetDbColums(this DbContext dbContext, Type clrEntityType)
    {
        var dbServices = dbContext.GetService<IDbContextServices>();
        var relationalDbServices = dbServices.DatabaseProviderServices as IRelationalDatabaseProviderServices;
        var annotationProvider = relationalDbServices.AnnotationProvider;
        var typeMapper = relationalDbServices.TypeMapper;

        var entityType = dbContext.Model.FindEntityType(clrEntityType);

        // Not needed here, just an example 
        var tableMap = annotationProvider.For(entityType);
        var tableName = tableMap.TableName;
        var tableSchema = tableMap.Schema;

        return from property in entityType.GetProperties()
               let columnMap = annotationProvider.For(property)
               let columnTypeMap = typeMapper.FindMapping(property)
               select new DbColumnInfo
               {
                   Name = columnMap.ColumnName,
                   Type = columnTypeMap.StoreType
               };
    }
}