如何将Google输入的数字字符串转换为整数作为存储到MySql DB中？

Question

我想将google输入类型的数字存储到其列为Integer的数据库中。 当我想将其转换为整数时，出现错误，提示输入字符串格式不正确，该如何解决此问题？

MySqlConnection con = new MySqlConnection("Server=syits03-pc;Database=Demo;Uid=root;Pwd=kbabu4668;CharSet=utf8;");
con.Open();
MySqlCommand cmd = new MySqlCommand("insert into tblnew(str,num,numstr) values(@str,@num,@numstr)", con);
cmd.Parameters.AddWithValue("@str", textBox1.Text);
MySqlCommand cmd1= new MySqlCommand("Select str from tblnew where id=1",con);
cmd.Parameters.AddWithValue("@num", Convert.ToInt32(cmd1.ExecuteScalar().ToString()));
cmd.Parameters.AddWithValue("@numstr", textBox3.Text);
object obj= cmd.ExecuteNonQuery();
con.Close();
if (obj != null)
{
    MessageBox.Show("Inserted");
}

Answer 1

看起来您的cmd.executescalar有时可能返回null，有时它会由tostring（）函数转换为“”，这可能是错误原因，如果您不确定输入的输入是否正确，则可以始终尝试使用int .TryParse（）请在使用前阅读有关该函数的信息

Answer 2

尝试using (SqlConnection con = new SqlConnection("Server = syits03 - pc; Database = Demo; Uid = root; Pwd = kbabu4668; CharSet = utf8; ")) { SqlCommand cmd1 = new SqlCommand("Select top 1 str from tblnew where id -1", con); string num = cmd1.ExecuteScalar().ToString(); string cmdText = string.Concat("insert into tblnew(str, num, numstr) values(", textBox1.Text, ",", num, ",", textBox3.Text, ")"); SqlCommand cmd = new SqlCommand(cmdText, con); cmd.ExecuteNonQuery(); } using (SqlConnection con = new SqlConnection("Server = syits03 - pc; Database = Demo; Uid = root; Pwd = kbabu4668; CharSet = utf8; ")) { SqlCommand cmd1 = new SqlCommand("Select top 1 str from tblnew where id -1", con); string num = cmd1.ExecuteScalar().ToString(); string cmdText = string.Concat("insert into tblnew(str, num, numstr) values(", textBox1.Text, ",", num, ",", textBox3.Text, ")"); SqlCommand cmd = new SqlCommand(cmdText, con); cmd.ExecuteNonQuery(); } using (SqlConnection con = new SqlConnection("Server = syits03 - pc; Database = Demo; Uid = root; Pwd = kbabu4668; CharSet = utf8; ")) { SqlCommand cmd1 = new SqlCommand("Select top 1 str from tblnew where id -1", con); string num = cmd1.ExecuteScalar().ToString(); string cmdText = string.Concat("insert into tblnew(str, num, numstr) values(", textBox1.Text, ",", num, ",", textBox3.Text, ")"); SqlCommand cmd = new SqlCommand(cmdText, con); cmd.ExecuteNonQuery(); }你应该考虑的一些可能的问题是：

• 如果cmd1没有返回任何内容，因此将空白值传递给@num怎么办？
• cmd.ExecuteNonQuery（）并非要返回任何内容，因此将其分配给对象可能不是最好的主意。 相反，您可以将其放在try / catch中。 例如， try { cmd.ExecuteNonQuery(); MessageBox.Show("Inserted"); } catch (Exception ex) { MessageBox.Show("Stored Proc failed with error: " + ex.ToString()); } try { cmd.ExecuteNonQuery(); MessageBox.Show("Inserted"); } catch (Exception ex) { MessageBox.Show("Stored Proc failed with error: " + ex.ToString()); }