What do I need to learn for accessing data from mssql database? - asp.net

Question

I am learning asp.net core mvc and API. I can simply work on it for CRUD operation. But, I get confused for accessing data from multiple tables like listing all categories with showing number of items each categories contains. What I need to learn for example Lina, entity framework code first, ado.net? I am currently using entity framework code first.
Thanks

Answer 1

Learn Dapper a simple object mapper for .NET.
What I Understood from your problem is that you have multiple tables and you want to query them and map the query result in your c# or vb code.Here I will show simple mapping of query result to c# objects.
Suppose you have three tables category_1,category_2 and category_3.
Lets say each table have two columns named itemName and ItemValue.
Lets create c# class corresponding to each table.
class category_1{
string ItemName {get;set};
int ItemValue {get;set;};
}
class category_2{
string ItemName {get;set};
int ItemValue {get;set;};
}
class category_3{
string ItemName {get;set};
int ItemValue {get;set;};
}
Suppose your querying three tables and map the result of query to respective object in c#.
let our sql query be as follows:
string sql = #"select * from category_1;select * from category_2;select * from category_3;"
Here we have three select statements and each select statement will give you result of respective table.Lets query the above sql to database using dapper and map them to c# object as follows.
List<category_1> lstCotegory1 = new List<category_1>();
List<category_2> lstCotegory2 = new List<category_2>();
List<category_3> lstCotegory3 = new List<category_3>();
using (var multi = connection.QueryMultiple(sql))
{
lstCotegory1 = multi.Read<category_1>().ToList(); // map first select statement
lstCotegory2 = multi.Read<category_2>().ToList(); // map second select statement
lstCotegory3 = multi.Read<category_3>().ToList(); // map third select statement.
}
This is how you can return results of multiple queries and map them to appropriate object. I know you can do better than this but to understand we have to go with simple example.Hope this will help.