/// <summary>
/// 根据指定表达式取表别名
/// </summary>
/// <param name="exp">表达式</param>
/// <remarks>
/// t=>t.Id
/// t.Id
/// </remarks>
public string GetTableAlias(Expression exp)
{
// p=>p.p
// p=>p.Id
// p=>p.t.Id
// p.Id
// p.t.Id
// p.t
// <>h__TransparentIdentifier0.p.Id
XfwException.Check.NotNull(exp, "exp");
string key = TableAliasCache.GetTableAliasKey(exp);
return(this.GetTableAlias(key));
}
private static string GetTableAliasKey(Expression exp)
{
if (exp == null)
{
return(null);
}
Expression expression = exp;
//c
if (exp.NodeType == ExpressionType.Constant)
{
return(null);
}
// p
ParameterExpression paramExp = expression as ParameterExpression;
if (paramExp != null)
{
return(paramExp.Name);
}
// a=>a.Id
LambdaExpression lambdaExp = expression as LambdaExpression;
if (lambdaExp != null)
{
expression = lambdaExp.Body.ReduceUnary();
}
// a.Id
// t.a
// t.t.a
// t.a.Id
MemberExpression memExp = expression as MemberExpression;
if (memExp == null)
{
return(TableAliasCache.GetTableAliasKey(expression));
}
if (memExp.IsVisitable())
{
return(TableAliasCache.GetTableAliasKey(memExp.Expression));
}
return(memExp.Member.Name);
}