c# - SqlParameter 的正确语法

Question

我正在尝试转换:

command.Parameters.Add (new SqliteParameter (DbType.Int32) { Value = id });

到一个普通的 SqlParameter :

command.Parameters.Add(new SqlParameter(DbType.Int32) { Value = id });

除了这一行，我现在已经设法转换了每一行，但我遇到了这些错误:

Error   3   Argument 1: cannot convert from 'System.Data.DbType' to 'object[]'
Error   2   The best overloaded method match for 'System.Data.SqlClient.SqlParameter.SqlParameter(object[])' has some invalid arguments

完整功能代码:

public User GetUser(int id)
{
    var u = new User();
    lock (locker)
    {
        connection = new SqlConnection("Data Source=" + path + ";Initial Catalog=DB;User ID=sa;Password=***********th");
        connection.Open();
        using (var command = connection.CreateCommand())
        {
            command.CommandText = "Select * from tblUsers WHERE UserID = ?";
            command.Parameters.Add(new SqlParameter(DbType.Int32) { Value = id });
            var r = command.ExecuteReader();
            while (r.Read())
            {
                u = FromReader(r);
                break;
            }
        }
        connection.Close();
    }
    return u;
}

Answer 1

我觉得你在看这个；

command.Parameters.Add(new SqlParameter("@YourParameterName", SqlDbType.Int32).Value = id;

编辑您的问题后；

您可以使用 AddWithValue方法。 Add(String, Object) method已经过时了。喜欢；

command.CommandText = "Select * from tblUsers WHERE UserID = @id";
command.Parameters.AddWithValue("@id", id);

如果您使用 SQL Server 作为数据库，您应该命名您的参数，将其添加到具有相同名称的 AddWithValue。

当您使用 OleDbCommand 时，参数的顺序很重要。因为作为MSDN说:

The OLE DB .NET Provider does not support named parameters for passing parameters to an SQL statement or a stored procedure called by an OleDbCommand when CommandType is set to Text. In this case, the question mark (?) placeholder must be used. For example:

SELECT * FROM Customers WHERE CustomerID = ?

Therefore, the order in which OleDbParameter objects are added to the OleDbParameterCollection must directly correspond to the position of the question mark placeholder for the parameter in the command text.