是否可以使用JoinSqlBuilder進行分頁？

Question

我有一個非常正常的加入，我通過JoinSqlBuilder

var joinSqlBuilder = new JoinSqlBuilder<ProductWithManufacturer, Product>() 
        .Join<Product, Manufacturer>(sourceColumn: p => p.ManufacturerId, 
               destinationColumn: mf => mf.Id, 
               sourceTableColumnSelection: p => new { ProductId = p.Id, ProductName = p.Name }, 
               destinationTableColumnSelection: m => new { ManufacturerId = m.Id, ManufacturerName = m.Name }) 

當然創建，連接此創建可能會返回大量的行，所以我想用分頁 - 最好是在服務器端。但是，我無法在JoinSqlBuilder中找到任何可以讓我這樣做的東西？我錯過了什麼或JoinSqlBuilder不支持這（尚）？

Answer 1

如果您不使用MS SQL Server，我認爲以下方法可行。

var sql = joinSqlBuilder.ToSql(); 
var data = this.Select<ProductWithManufacturer>(
       q => q.Select(sql) 
         .Limit(skip,rows) 
      ); 

如果您正在使用MS SQL Server，它很可能會炸燬你。我正在努力將類似於此的更優雅的解決方案合併到JoinSqlBuilder中。以下是一個快速而骯髒的方法來完成你想要的。

我創建了以下擴展類：

public static class Extension 
{ 

    private static string ToSqlWithPaging<TResult, TTarget>(
     this JoinSqlBuilder<TResult, TTarget> bldr, 
     string orderColumnName, 
     int limit, 
     int skip) 
    { 
     var sql = bldr.ToSql(); 

     return string.Format(@" 
       SELECT * FROM (
        SELECT ROW_NUMBER() OVER (ORDER BY [{0}]) As RowNum, * 
         FROM (
          {1} 
          )as InnerResult 
         )as RowConstrainedResult 
        WHERE RowNum > {2} AND RowNum <= {3} 
      ", orderColumnName, sql, skip, skip + limit); 
    } 

    public static string ToSqlWithPaging<TResult, TTarget>(
     this JoinSqlBuilder<TResult, TTarget> bldr, 
     Expression<Func<TResult, object>> orderSelector, 
     int limit, 
     int skip) 
    { 

     var member = orderSelector.Body as MemberExpression; 
     if (member == null) 
      throw new ArgumentException(
       "TResult selector refers to a non member." 
       ); 

     var propInfo = member.Member as PropertyInfo; 
     if (propInfo == null) 
      throw new ArgumentException(
       "TResult selector refers to a field, it must be a property." 
       ); 

     var orderSelectorName = propInfo.Name; 

     return ToSqlWithPaging(bldr, orderSelectorName, limit, skip); 
    } 
} 

它的應用如下所示：

List<Entity> GetAllEntities(int limit, int skip) 
{ 
    var bldr = GetJoinSqlBuilderFor<Entity>(); 
    var sql = bldr.ToSqlWithPaging(
        entity => entity.Id, 
        limit, 
        skip); 
    return this.Db.Select<Entity>(sql); 
}