public static string GetStatement(Parameters parameters, Expression expression)
{
var expressionVisitor = new SelectExpressionVisitor(parameters);
expressionVisitor.VisitExpression(expression);
return(expressionVisitor.GetStatement());
}
internal void Visit()
{
Visit(expression);
//获取表名
Type elementType = null;
MethodCallExpression call = expression as MethodCallExpression;
while (true)
{
var exp = call.Arguments[0];
if (exp is MethodCallExpression)
{
call = exp as MethodCallExpression;
continue;
}
if (exp is ConstantExpression)
{
var constExp = exp as ConstantExpression;
elementType = constExp.Type.GetGenericArguments()[0];
break;
}
throw new Exception("获取表达式树表名的时候出错");
}
var entityInfo = _entityManager.GetEntity(elementType);
//var tableAttr = (TableAttribute)elementType.GetCustomAttributes(_tableAttrType, true).FirstOrDefault();
//string tableName = elementType.Name + "s";
//if (tableAttr != null)
//{
// tableName = tableAttr.TableName;
//}
StringBuilder sb = new StringBuilder("select ");
Dictionary<string, string> aliaTableNameMap = new Dictionary<string, string>();
//先执行Select，必须执行
if (_expressionDict.ContainsKey("Select"))
{
selectorVisitor = new SelectExpressionVisitor(entityInfo, _expressionDict["Select"]);
selectorVisitor.Visit();
_columns = string.Join(",", selectorVisitor.Columns);
_alias = selectorVisitor.Alias;
aliaTableNameMap = selectorVisitor.TableInfos;
selectorVisitor.ClearResult();
}
else
{
var type = expression.Type.GetGenericArguments()[0];
var pis = ExpressionReflector.GetProperties(type).Values;
_alias = pis.Select(x => x.Name).ToList();
_columns = string.Join(",", _alias.Select(x => "[" + x + "]"));
aliaTableNameMap.Add(entityInfo.TableName, entityInfo.TableName);
}
//再执行Where，可以没有
//Parameters = new Dictionary<string, object>();
//if (_expressionDict.ContainsKey("Where"))
//{
// var whereVisitor = new WhereExpressionVisitor(aliaTableNameMap, _expressionDict["Where"]);
// whereVisitor.Visit();
// condition = whereVisitor.Condition;
// Parameters = whereVisitor.Parameters;
//}
////先解析为查询
StringBuilder childSelect = new StringBuilder("select ");
childSelect.Append(string.Join(",", _columns));
//childSelect.Append(" from " + tableName);
//是否需要包装成子查询
if (selectorVisitor != null && selectorVisitor.NeedWrapSelect)
{
//拼接主查询
sb.Append(string.Join(" , ", _alias));
sb.AppendFormat(" from ({0}) t ", childSelect.ToString());
}
else
{
sb = childSelect;
}
if (!string.IsNullOrEmpty(condition))
{
sb.Append(" where ");
sb.Append(condition);
}
CommandText = sb.ToString();
}
public override void VisitSelectClause(SelectClause selectClause, QueryModel queryModel)
{
m_selectPart = SelectExpressionVisitor.GetStatement(m_parameters, selectClause.Selector);
base.VisitSelectClause(selectClause, queryModel);
}
