/// <summary>
/// 创建分组表达式。
/// </summary>
/// <param name="source">源表达式。</param>
/// <param name="keypro">分组键的CLR描述对象。</param>
/// <param name="key">分组键表达式。</param>
/// <param name="item">单元项表达式，用于自定义创建分组项表达式。</param>
public DbGroupByExpression(DbUnitTypeExpression source, PropertyInfo keypro, DbExpression key, DbUnitItemTypeExpression item)
: base(source.ClrType, new DbGroupItemExpression(item))
{
Source = source;
KeyProperty = keypro;
Key = key;
}
/// <summary>
/// 创建SELECT查询表达式。
/// </summary>
/// <param name="source">源数据单元表达式。</param>
/// <param name="itemType">单元数据项CLR类型。</param>
public DbSelectExpression(DbUnitTypeExpression source, DbUnitItemTypeExpression itemType)
: base(typeof(IQueryable <>).MakeGenericType(itemType.ClrType), source, itemType)
{
}
/// <summary>
/// 创建笛卡尔积连接表达式。
/// </summary>
/// <param name="source">源表达式。</param>
/// <param name="target">目标表达式。</param>
/// <param name="newExp">连接后输出的项表达式。</param>
public DbCrossJoinExpression(DbUnitTypeExpression source, DbUnitTypeExpression target, DbUnitItemTypeExpression newExp)
: base(typeof(IQueryable <>).MakeGenericType(newExp.ClrType), source, newExp)
{
Target = target;
}
/// <summary>
/// 创建内连接操作表达式。
/// </summary>
/// <param name="source">源表达式。</param>
/// <param name="target">目标表达式。</param>
/// <param name="left">左端匹配键表达式。</param>
/// <param name="right">左端匹配键表达式。</param>
/// <param name="newExp">连接后输出的新对象表达式，该成员是LINQ连接体系中所必须的。</param>
public DbInnerJoinExpression(DbUnitTypeExpression source, DbUnitTypeExpression target, DbExpression left, DbExpression right, DbUnitItemTypeExpression newExp)
: base(typeof(IQueryable <>).MakeGenericType(newExp.ClrType), source, newExp)
{
Target = target;
switch (left.ExpressionType)
{
case EExpressionType.MemberAccess:
KeyPairs = new DbJoinKeyPairExpression[] { new DbJoinKeyPairExpression(left, right) };
break;
case EExpressionType.New:
KeyPairs = (from a in ((DbNewExpression)left).Members
join b in ((DbNewExpression)right).Members on a.Key equals b.Key
select new DbJoinKeyPairExpression(a.Value, b.Value)).ToArray();
break;
default:
throw new NotSupportedException(string.Format(Res.NotSupportedExpressionParseInnerJoinKeyPairs, left.ExpressionType));
}
}
/// <summary>
/// 创建单元类型表达式。
/// </summary>
/// <param name="type">数据项CLR类型。</param>
/// <param name="itemType">数据项表达式。</param>
public DbUnitTypeExpression(Type type, DbUnitItemTypeExpression itemType)
{
ClrType = type;
ReplaceItem(itemType);
}
/// <summary>
/// 替换当前的数据项表达式。
/// </summary>
/// <param name="item">替换表达式。</param>
/// <returns>当前单元表达式。</returns>
public DbUnitTypeExpression ReplaceItem(DbUnitItemTypeExpression item)
{
Item = item;
item.Unit = this;
return(this);
}
/// <summary>
/// 初始化数据集操作。
/// </summary>
/// <param name="type">数据集的元素CLR类型。</param>
/// <param name="source">操作的单元表达式。</param>
/// <param name="itemType">单元项表达式。</param>
public DbSetOperationExpression(Type type, DbUnitTypeExpression source, DbUnitItemTypeExpression itemType)
: base(type, itemType)
{
Source = source;
}