ComiServMirror/Extensions/DatabaseExtensions.cs

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.ChangeTracking;
using System.Runtime.CompilerServices;

//https://stackoverflow.com/a/42467710/25956209
//https://archive.ph/RvjOy
namespace ComiServ.Extensions
{
    public static class DatabaseExtensions
    {
        //with a compound primary key, `ignorePrimaryKey` will ignore all of them
        public static int InsertOrIgnore<T>(this DbContext context, T item, bool ignorePrimaryKey = false)
        {
            var entityType = context.Model.FindEntityType(typeof(T));
            var tableName = entityType.GetTableName();
            //var tableSchema = entityType.GetSchema();

            var cols = entityType.GetProperties()
                .Where(c => !ignorePrimaryKey || !c.IsPrimaryKey())
                .Select(c => new {
                    Name = c.GetColumnName(),
                    //Type = c.GetColumnType(),
                    Value = c.PropertyInfo.GetValue(item)
                })
                .ToList();
            var query = "INSERT OR IGNORE INTO " + tableName
                + " (" + string.Join(", ", cols.Select(c => c.Name)) + ") " +
                "VALUES (" + string.Join(", ", cols.Select((c,i) => "{" + i + "}")) + ")";
            var args = cols.Select(c => c.Value).ToArray();
            var formattable = FormattableStringFactory.Create(query, args);
            return context.Database.ExecuteSql(formattable);
        }
        public static int InsertOrIgnore<T>(this DbContext context, IEnumerable<T> items, bool ignorePrimaryKey = false)
        {
            var entityType = context.Model.FindEntityType(typeof(T));
            var tableName = entityType.GetTableName();
            //var tableSchema = entityType.GetSchema();

            var colProps = entityType.GetProperties().Where(c => !ignorePrimaryKey || !c.IsPrimaryKey()).ToList();
            var colNames = colProps.Select(c => c.Name).ToList();
            if (colNames.Count == 0)
                throw new InvalidOperationException("No columns to insert");
            var rows = items
                .Select(item =>
                    colProps.Select(c =>
                        c.PropertyInfo.GetValue(item))
                    .ToList())
                .ToList();
            int count = 0;
            var query = "INSERT OR IGNORE INTO " + tableName
                + "(" + string.Join(',', colNames) + ")"
                + "VALUES" + string.Join(',', rows.Select(row =>
                    "(" + string.Join(',', row.Select(v => "{" 
                    + count++
                    + "}")) + ")"
                ));
            var args = rows.SelectMany(row => row).ToArray();
            var formattable = FormattableStringFactory.Create(query, args);
            return context.Database.ExecuteSql(formattable);
        }
    }
}