Question

我正在尝试使用ado.net连接将字典中存在的详细信息存储到SQL Server中，但是当我尝试向数据库中插入值时出现未找到键的异常。

if(option==2)
    {
        SqlConnection con = new SqlConnection("Data Source=.;Database=Demo;Integrated Security=SSPI");
        con.Open();
        SqlCommand cmd = new SqlCommand("INSERT INTO tnlFourWheeler(Vno, years, cost,color,fuel,doors,seats) " +
            " VALUES (@Vno, @years, @cost,@color,@fuel,@doors,@seats)", con);
        for (int i = 0; i < keyValuePairs.Count; i++)
        {
            FourWheeler t = (FourWheeler)keyValuePairs[i];
            cmd.Parameters.AddWithValue("@Vno", t.vehicleNumber);
            cmd.Parameters.AddWithValue("@years", t.numberOfYears);
            cmd.Parameters.AddWithValue("@cost", t.cost);
            cmd.Parameters.AddWithValue("@color", t.color);
            cmd.Parameters.AddWithValue("@fuel", t.fuelType);
            cmd.Parameters.AddWithValue("@doors", t.doors);
            cmd.Parameters.AddWithValue("@seats", t.seats);
            cmd.ExecuteNonQuery();

        }
        con.Close();

Answer 1

Dictionary<TKey,TValue>未通过array-index进行索引，而是通过键进行了索引。

执行此操作（将TKey替换为实际的TKey）：

foreach( KeyValuePair<TKey,FourWheeler> kvp in keyValuePairs )
{
    FourWheeler t = kvp.Value;

    // ...
}

或者：

foreach( TKey key in keyValuePairs.Keys )
{
    FourWheeler t = keyValuePairs[key];

    // ...
}

如何解决字典集合中未找到键的异常

1 个答案: