/// <summary>
/// 转换成Sql语句
/// </summary>
/// <returns></returns>
public override string ToSql()
{
var orders = new Strings();
var columns = new List <string>();
foreach (var pair in sorts)
{
var exp = pair.Key;
var sql = SqlExpressionVistor.Visit(exp, privoder);
if (!columns.Contains(exp.ToString()))
{
var sc = pair.Value ? "ASC" : "DESC";
columns.Add(exp.ToString());
orders.Add(string.Format("{0} {1}", sql, sc));
}
else
{
throw Error.Exception("排序依据列表中的依据不能重复：" + sql);
}
}
if (columns.Any())
{
return(" ORDER BY " + orders);
}
return(string.Empty);
}
protected void GetMembers(Expression expression, Strings strs, MemberInfo member, string path = null)
{
if (expression is MemberExpression || expression is BinaryExpression)
{
var sql = SqlExpressionVistor.Visit(expression, this);
var name = member.Name;
if (!path.IsNullOrWhiteSpace())
{
name = path + "-" + name;
}
var field = EscapeSqlIdentifier(name);
strs.Add(string.Format("{0} AS {1}", sql, field));
namedType.Add(member, sql);
return;
}
var newExp = expression as NewExpression;
if (expression is MemberInitExpression)
{
var exp = (MemberInitExpression)expression;
newExp = exp.NewExpression;
foreach (var binding in exp.Bindings)
{
var me = binding as MemberAssignment;
GetMembers(me.Expression, strs, binding.Member, path);
}
}
var inits = newExp.Arguments;
var mems = newExp.Members;
for (int i = 0; i < mems?.Count; i++)
{
if (inits[i] is MemberExpression || inits[i] is BinaryExpression)
{
GetMembers(inits[i], strs, mems[i], path);
}
else if (inits[i] is NewExpression)
{
var _path = mems[i].Name;
if (!path.IsNullOrWhiteSpace())
{
_path = path + "-" + _path;
}
GetMembers(inits[i], strs, null, _path);
}
else
{
throw Error.NotSupportedException("不支持复杂的类型初始化。");
}
}
}
/// <summary>
/// 获取子查询字段部分，每个字段都带着L-或R-前缀，表示字段路径
/// </summary>
/// <returns></returns>
protected override void SetInnerFields()
{
if (tableMeta.IsSimpleType())
{
var sql = SqlExpressionVistor.Visit(this.selector, this);
_fieldsPart = string.Format("{0} AS Field", sql);
namedType.AddDefault(sql);
}
else
{
var strs = new Strings();
GetMembers(selector.Body, strs, null);
_fieldsPart = strs.ToString();
}
}
/// <summary>
/// 聚合函数
/// </summary>
/// <typeparam name="TAggregate"></typeparam>
/// <param name="selector"></param>
/// <param name="aggregateName"></param>
/// <returns></returns>
private TAggregate Aggregate <TAggregate>(Expression <Func <T, TAggregate> > selector, string aggregateName)
{
this.parameterIndex = 0;
var _tableName = GetTableNameOrInnerSql();
var columnName = SqlExpressionVistor.Visit(selector, this);
var sql = string.Format("SELECT {5}({4}{3}) FROM {0} {1} {2}", _tableName, this.GetWherePart(), this.GetOrderPart(), columnName, this.DistinctPart, aggregateName);
var value = Context.ExecuteScalar(sql, this.DbParameters);
if (value == DBNull.Value)
{
if (typeof(TAggregate).IsValueType && (aggregateName == "SUM" || aggregateName == "AVG"))
{
return(default(TAggregate));
}
throw new XDataException("聚合结果为DBNull。");
}
return((TAggregate)value);
}
protected override object InitFieldsPart()
{
if (fieldsPart.IsNullOrWhiteSpace())
{
if (tableMeta.IsSimpleType())
{
var sql = SqlExpressionVistor.Visit(this.resultSelector, this);
fieldsPart = string.Format("{0} AS Field", sql);
namedType.AddDefault(sql);
}
else
{
var strs = new Strings();
GetMembers(resultSelector.Body, strs, null);
fieldsPart = strs.ToString();
}
}
return(fieldsPart);
}
/// <summary>
/// 转换成Sql语句
/// </summary>
/// <returns></returns>
public override string ToSql()
{
var wb = SqlExpressionVistor.Visit(whereExpression, privoder);
return(string.Format(" WHERE {0}", wb));
}
