c# - 数据表 C# 输入字符串的格式不正确

Question

我的代码:

DataTable dt = new DataTable();
mySqlDataAdapter.Fill(dt);
int socot = dt.Rows.Count;
for (int i = 0; i < socot; i++)
{
    String dn = dt.Rows[i][1].ToString();
    String gduan = "SELECT tennha FROM duannha WHERE id=@id";
    MySqlCommand cmd = new MySqlCommand();
    cmd.Connection = conn;
    cmd.CommandText = gduan;
    cmd.Parameters.AddWithValue("@id", dn);
    String gtennha = cmd.ExecuteScalar().ToString();
    dt.Rows[i][1] = gtennha;
}

当我运行代码时，我收到一个错误。请帮我修复它。

Answer 1

Expected Type as Int32

如果 gtennha 包含数字，您可以将其解析为 int。有了更多的保障:

var gtennha = cmd.ExecuteScalar();
try 
{
   if(gtennha != null)
      dt.Rows[i][1] = int.Parse(gtennha.ToString());
   else 
      Console.WriteLine("Error: Query didn't return a result.");
} 
catch(FormatException ex)
{
   Console.WriteLine("Error: Couldn't parse 'gtennha' to a number.");
   /* more error handling */
}