c# - 将条件构建的 SQL where 子句转换为 LINQ

Question

所以我在这里没有看到真正回答这个问题的问题。这是一个关于 linq 的新手问题，但我想知道是否可以将以下 sql 查询(使用 C# 构建)转换为 linq 查询:

public void DoSomeQuery(bool whereCriteria1, bool whereCriteria2)
{
    string sqlQuery = "SELECT p.*";
    string fromClause = " FROM person p";
    string whereClause = " WHERE ";

    if (whereCriteria1)
    {
        fromClause += ", address a";
        whereClause += " p.addressid = a.addressid and a.state = 'PA' and a.zip = '16127' "
    }

    if (whereCriteria2)
    {
        fromClause += ", color c";
        whereClause += " p.favoritecolorid = c.colorid and c.name = 'blue'"
    }

    // arbitrarily many more criteria if blocks could be here

    sqlQuery += fromClause + whereClause;

    // do stuff to run the query
}

这有意义吗？我有一堆 bool 变量，让我知道要添加哪个 where 子句条件。我想在 linq 中这样做，因为...这很丑陋。

Answer 1

var query = from p in persons select p;
if (whereCriteria1)
{
  query = from p in query 
  join a in address on p.addressid equals a.addressid 
  where a.state = 'PA' 
  where a.zip = '16127'
  select p;
}
if (whereCriteria2)
{
  query = from p in query
  join c in colors on p.favoritecolorid equals c.colorid 
  where c.name = 'blue'
  select p;
}