/// <summary>
/// Combines the first predicate with the second using a logical "or". Short-circuits if either expression is constant
/// </summary>
/// <typeparam name="T">The input type for both predicates</typeparam>
/// <param name="first">The first predicate</param>
/// <param name="second">The second predicate</param>
/// <returns>An expression representing a logical "or" between both predicates</returns>
public static Expression <Func <T, bool> > Or <T>(this Expression <Func <T, bool> > first,
Expression <Func <T, bool> > second)
{
if (ExpressionUtility.IsConstant(first, false))
{
return(second);
}
if (ExpressionUtility.IsConstant(second, false))
{
return(first);
}
if (ExpressionUtility.IsConstant(first, true) || ExpressionUtility.IsConstant(second, true))
{
return(True <T>());
}
return(first.Combine(second, (a, b) => a || b));
}
/// <summary>
/// 查询条件表达式转换为谓词组的扩展方法
/// </summary>
/// <typeparam name="TEntity">实体类型</typeparam>
/// <typeparam name="TPrimaryKey">实体主键类型</typeparam>
/// <param name="expression">查询条件表达式</param>
/// <returns>查询条件谓词组</returns>
public static IPredicate ToPredicateGroup <TEntity, TPrimaryKey>(
this Expression <Func <TEntity, bool> > expression) where TEntity : class
{
if (expression == null)
{
return(null);
}
if (ExpressionUtility.IsConstant(expression, true))
{
return(null);
}
if (ExpressionUtility.IsConstant(expression, false))
{
return(null);
}
IPredicate pg = QueryBuilder <TEntity> .FromExpression(expression);
return(pg);
}