.NET Core 3 / EF.Core 3：`QueryModelGenerator`、`RelationalQueryModelVisitor` 等发生了什么

Question

我不知道发生了什么事：QueryModelGenerator，RelationalQueryModelVisitor和queryCompilationContext.CreateQuerymodelVisitor()一切似乎都烟消云散了。

我有以下代码，但我无法尝试将其从 2.2 转换为 .NET Core 3

public static string ToSql<TEntity>(this IQueryable<TEntity> query, DbContext dbCtx)
{
    var modelGenerator = dbCtx.GetService<IQueryModelGenerator>();
    var queryModel = modelGenerator.ParseQuery(query.Expression);
    var databaseDependencies = dbCtx.GetService<DatabaseDependencies>();
    var queryCompilationContext = databaseDependencies.QueryCompilationContextFactory.Create(false);
    var modelVisitor = (RelationalQueryModelVisitor) queryCompilationContext.CreateQueryModelVisitor();
    modelVisitor.CreateQueryExecutor<TEntity>(queryModel);
    var sql = modelVisitor.Queries.FirstOrDefault()?.ToString();
    return sql;
}

Answer 1

在 EF 3 中不再受支持。

现在怎么做

    public static string ToSql<TEntity>(this IQueryable<TEntity> query)
    {
        var enumerator = query.Provider.Execute<IEnumerable<TEntity>>(query.Expression).GetEnumerator();
        var enumeratorType = enumerator.GetType();
        var selectFieldInfo = enumeratorType.GetField("_selectExpression", BindingFlags.NonPublic | BindingFlags.Instance) ?? throw new InvalidOperationException($"cannot find field _selectExpression on type {enumeratorType.Name}");
        var sqlGeneratorFieldInfo = enumeratorType.GetField("_querySqlGeneratorFactory", BindingFlags.NonPublic | BindingFlags.Instance) ?? throw new InvalidOperationException($"cannot find field _querySqlGeneratorFactory on type {enumeratorType.Name}");
        var selectExpression = selectFieldInfo.GetValue(enumerator) as SelectExpression ?? throw new InvalidOperationException($"could not get SelectExpression");
        var factory = sqlGeneratorFieldInfo.GetValue(enumerator) as IQuerySqlGeneratorFactory ?? throw new InvalidOperationException($"could not get IQuerySqlGeneratorFactory");
        var sqlGenerator = factory.Create();
        var command = sqlGenerator.GetCommand(selectExpression);
        var sql = command.CommandText;
        return sql;
    }

在此处查看更多信息：https : //stackoverflow.com/a/51583047/196698 https://gist.github.com/rionmonster/2c59f449e67edf8cd6164e9fe66c545a#gistcomment-3059688