How to store value in variable joining two tables - sql

Question

I am still learning SQL, but as I got stuck in these doubt I wrote it here.
Actually I want print a table for list of details which hold a column for "Description". Now this data is retrieving from tblBillDetails. and in tblBillDetails there is no column or field of "Description. Now there is another field which is tblProduct here I have column "Name" & "Id".
So I want something like "Description = tblProduct.Name where tblBillDetails.FunctionId == tblProduct.Id
code--->
.cs file
public class BillDetail
{
public long Id { get; set; }
public long BillId { get; set; }
public int FunctionType { get; set; }
public long FunctionId { get; set; }
public long VatId { get; set; }
public int Quantity { get; set; }
public int Points { get; set; }
public decimal TotalValue { get; set; }
public decimal FreeValue { get; set; }
public DateTime SaleDateTime { get; set; }
public long BalanceId { get; set; }
public decimal RunningBalance { get; set; }
}
repositoy .cs file
public Task<BillDetail> SingleAsync(Guid shardKey, long BillDetailId)
{
return _billDetailDataAccess.SingleAsync(shardKey, BillDetailId);
}
DataAccess .cs file
public async Task<BillDetail> SingleAsync(Guid shardKey, long BillDetailId)
{
string sql = #"SELECT [Id]
,[TenantClientId]
,[BillId]
,[FunctionType]
,[FunctionId]
,[VatId]
,[Quantity]
,[Points]
,[TotalValue]
,[FreeValue]
,[SaleDateTime]
,[BalanceId]
,[RunningBalance]
,[Archived]
FROM [dbo].[tblBillDetail]
WHERE [tblBillDetail].[Id] = #BillDetailId
;";
await _context.OpenConnectionForKeyAsync(shardKey);
return await _context.Connection.QueryFirstOrDefaultAsync<BillDetail>(sql, new { BillDetailId });
}