Query an Entity Framework entity without knowing the object type (class/table) in advance

Question

I'm wondering, if it's even possible in the first place, how I would go about querying the database (using EF) using an ID and a table name.

For example, writing a function as:

QueryDynamicData(string tableName, long entityID){return GetItem(tableName, entityID);}

And could be called like:

var entry = QueryDynamicData("Person", 143);

To clarify, this is for a MVC ASP.Net project using Entity Frameworks.

Thanks in advance!

EDIT:

Following the example from @JPVenson, I came up with the following code. Note that it returns a list of Dictionaries, even though Id is unique, since I'm thinking ahead to when we may want to get all results for a dynamic table instead of just by Id. (This is only proof of concept level)

public List<Dictionary<string, object>> QueryDynamicData(string table, int entityID)
    {
        try
        {
            //Get the table desired based on the table name passed
            PropertyInfo dbSetInfo = DBContext.GetType().GetProperties().FirstOrDefault(p => p.Name.ToLower().Equals(table.ToLower()));

            //Return all results from the table into IQueryable set where Id = entityID passed
            IQueryable anyDbSet = ((IQueryable)dbSetInfo.GetValue(DBContext)).Where("Id=" + entityID);

            List<Dictionary<string,object>> listObjects = new List<Dictionary<String, Object>>();

            //Iterate through results
            foreach (Object entity in anyDbSet)
            {
                //Create dictionary of Field Name, Field Value from results
                Dictionary<string, object> listDBValues = entity.GetType().GetProperties().ToDictionary(propertyInfo => propertyInfo.Name, propertyInfo => propertyInfo.GetValue(entity));

                //Add dictionary to list of dictionaries - useful for returning list of found results instead of just one
                listObjects.Add(listDBValues);
            }

            //Return list of dictionaries
            return listObjects;
        }
        catch (Exception e) { }
        return null;
    }

Answer 1

Yes you can. There is a blog from ScottGu

https://weblogs.asp.net/scottgu/dynamic-linq-part-1-using-the-linq-dynamic-query-library

(MS Version of DynamicLinq https://github.com/kahanu/System.Linq.Dynamic/wiki)

that contains the wiki for a lib called DynamicLinq. I'm using it currently in a Project and it will fit your approach.

You still have to wrap it and use some Reflection to build a proper IQueryable but it does a lot of work for you

Edit Code Example

With some reflection you can access your dbSet like this (Untested Pseudocode!):

public object[] QueryDynamicData(string table, int entityId) {    
   //Your DbContext that contains all of your 
   var dbContext = new FooBaa() 
   //Get the DbSet in your DbContext that matches the "Table" name.
   //You are searching for the generic parameter of the DbSet
   var dbSetInfo = dbContext.GetType().GetProperties().FirstOrDefault(e => e.GetGenericArguments().Any(f => f.Name.Equals(table)); 
   //Now get the DbSet from the DbContext and cast it to an IQueryabe
   IQueryable anyDbSet = (IQueryable)dbSetInfo.GetValue(dbContext);
   //Use Dynamic Linq to create a Query that selects an ID
   //warning SQL-Injection possible checkout the 2nd argument of type IDictionary
   return anyDbSet.Where("Id=" + entityId).ToArray();
}