当尝试获取传递给函数的表上的列时，出现错误

Question

Problem

when try to get columns exist on table passed to function I get error

Database Facade doesn't contain definition for SqlQuery and no accessible extension method SqlQuery

I work on asp.net core 2.1 web api code first

i try to design function give here table name and it will return columns exist on this

table but i get compile error

Database Facade doesn't contain definition for SqlQuery and no accessible extension method SqlQuery

so How to solve that Error

public class TabDbContext : DbContext
    {
        public TabDbContext(DbContextOptions<TabDbContext> options)
: base(options)
        { }

        public DbSet<Employee> Employees { get; set; }
        public DbSet<Employee> Departments { get; set; }

ON controller API I do as following :

public class EmployeesController : ControllerBase
    {
        private readonly TabDbContext _context;

        public EmployeesController(TabDbContext context)
        {
            _context = context;
        }
 public List<string> GetColumnNames(string tablename)
        {

                var sql = "select COLUMN_NAME from information_schema.COLUMNS where table_name = @TableName";
                SqlParameter sqlParameter = new SqlParameter("TableName", tablename);
                var query = _context.Database.SqlQuery<string>(sql, sqlParameter).ToList();
                return query;

        }

Expected Result

Employees Table have two columns EmployeeId,EmployeeName

calling function as GetColumnNames(Employees)

will return

EmployeeId

EmployeeName

Answer 1

You can use the FromSql extension method to begin a LINQ query based on a raw SQL query in EF Core 2.1 :

https://docs.microsoft.com/en-us/ef/core/querying/raw-sql

Then your code would modify like :

var sqlParameter = new SqlParameter("TableName", tablename);
var employees= _context.Employees
               .FromSql("select COLUMN_NAME from information_schema.COLUMNS where table_name = @TableName", sqlParameter )
               .ToList();