SqlCeCommand可以为空的值

Question

我的代码：

SqlCeConnection sql = new SqlCeConnection(@"Data Source=C:\DB.sdf");
sql.Open();
cmd = new SqlCeCommand("INSERT INTO xxx(aaa) VALUES(@aaa)", sql);
String param = null;  //doesn't work
//String param = "blah" //works
cmd.Parameters.AddWithValue("@aaa", param);
cmd.ExecuteNonQuery(); //(1)
sql.Close();

（1）在param为空时抛出异常。数据库允许collumn aaa中的值为null。如何在表xxx中插入null？

例外：
Parameterized query 'INSERT INTO xxx(aaa) VALUES(@aaa)' expects a parameter value which was not supplied.

Answer 1

请尝试使用DBNull.Value：

var param = DBNull.Value;

Answer 2

使用

var param = DBNull.Value;

null与DBNull

不同