当我执行查询时，我希望获得的结果存储在变量（a）中，然后我希望将该变量转换为int并乘以另一个文本框（textbox1）的值，并将其乘以存储在另一个文本框（textbox2）中。 继承了整个表格的代码
private void menustart_Load(object sender, EventArgs e)
{
// TODO: This line of code loads data into the 'cmsDataSet.menulist' table. You can move, or remove it, as needed.
String con = "datasource = localhost; port=3306;username=root;password=brianfdes93";
MySqlConnection mycon = new MySqlConnection(con);
//wine
string qw = "select wine from cms.menulist";
MySqlDataAdapter da = new MySqlDataAdapter(qw, mycon);
DataTable dt1 = new DataTable();
da.Fill(dt1);
foreach (DataRow row in dt1.Rows)
{
string wine = string.Format("{0}", row.ItemArray[0]);
comboBox1.Items.Add(wine);
}
//nvstarter
string qsnv = "select st_nonveg from cms.menulist";
MySqlDataAdapter da1 = new MySqlDataAdapter(qsnv, mycon);
DataTable dt2 = new DataTable();
da1.Fill(dt2);
foreach (DataRow row in dt2.Rows)
{
string nvs = string.Format("{0}", row.ItemArray[0]);
comboBox2.Items.Add(nvs);
}
//vstarter
string qsv = "select st_veg from cms.menulist";
MySqlDataAdapter da3 = new MySqlDataAdapter(qsv, mycon);
DataTable dt3 = new DataTable();
da3.Fill(dt3);
foreach (DataRow row in dt3.Rows)
{
string vs = string.Format("{0}", row.ItemArray[0]);
comboBox3.Items.Add(vs);
}
//rice n v
string qrnv = "select rice_nonveg from cms.menulist";
MySqlDataAdapter da4 = new MySqlDataAdapter(qrnv, mycon);
DataTable dtrnv = new DataTable();
da4.Fill(dtrnv);
foreach (DataRow row in dtrnv.Rows)
{
string rnv = string.Format("{0}", row.ItemArray[0]);
comboBox4.Items.Add(rnv);
}
// rice v
string qrv = "select rice_veg from cms.menulist";
MySqlDataAdapter da4i = new MySqlDataAdapter(qrv, mycon);
DataTable dtrv = new DataTable();
da4i.Fill(dtrv);
foreach (DataRow row in dtrv.Rows)
{
string rv = string.Format("{0}", row.ItemArray[0]);
comboBox4i.Items.Add(rv);
}
//nvgravy
string qgnv = "select g_nonveg from cms.menulist";
MySqlDataAdapter da5 = new MySqlDataAdapter(qgnv, mycon);
DataTable dtgnv = new DataTable();
da5.Fill(dtgnv);
foreach (DataRow row in dtgnv.Rows)
{
string gnv = string.Format("{0}", row.ItemArray[0]);
comboBox5.Items.Add(gnv);
}
//vgravy
string qgv = "select g_veg from cms.menulist";
MySqlDataAdapter da6 = new MySqlDataAdapter(qgv, mycon);
DataTable dtgv = new DataTable();
da6.Fill(dtgv);
foreach (DataRow row in dtgv.Rows)
{
string gv = string.Format("{0}", row.ItemArray[0]);
comboBox6.Items.Add(gv);
}
//sanv
string qsanv = "select s_nonveg from cms.menulist";
MySqlDataAdapter da7 = new MySqlDataAdapter(qsanv, mycon);
DataTable dtsanv = new DataTable();
da7.Fill(dtsanv);
foreach (DataRow row in dtsanv.Rows)
{
string sanv = string.Format("{0}", row.ItemArray[0]);
comboBox7.Items.Add(sanv);
}
//sav
string qsav = "select s_veg from cms.menulist";
MySqlDataAdapter da8 = new MySqlDataAdapter(qsav, mycon);
DataTable dtsav = new DataTable();
da8.Fill(dtsav);
foreach (DataRow row in dtsav.Rows)
{
string sav = string.Format("{0}", row.ItemArray[0]);
comboBox8.Items.Add(sav);
}
//dessert
string qd = "select dessert from cms.menulist";
MySqlDataAdapter da9 = new MySqlDataAdapter(qd, mycon);
DataTable dtd = new DataTable();
da9.Fill(dtd);
foreach (DataRow row in dtd.Rows)
{
string sav = string.Format("{0}", row.ItemArray[0]);
comboBox9.Items.Add(sav);
}
mycon.Close();
// to populate iod
int nxtorder;
String coni = "datasource = localhost; port=3306;username=root;password=brianfdes93";
MySqlConnection myconi = new MySqlConnection(coni);
string query = "select MAX(o_id) from cms.order";
MySqlCommand o = new MySqlCommand(query, myconi);
myconi.Open();
MySqlDataReader reader = o.ExecuteReader();
while (reader.Read())
{
if (reader.IsDBNull(reader.GetOrdinal("max(o_id)")))
{
nxtorder = 1;
tid.Text = Convert.ToString(nxtorder);
}
else
{
nxtorder = Convert.ToInt32(reader["max(o_id)"]);
tid.Text = Convert.ToString(nxtorder);
}
}
//to fill guest txtbox
}
private void button1_Click(object sender, EventArgs e)
{
starting s = new starting();
s.Show();
this.Close();
}
private void button2_Click(object sender, EventArgs e)
{
tabControl1.SelectedTab = tabPage3;
t1.Text = t11.Text;
t2.Text = t12.Text;
t3.Text = t13.Text;
t4.Text = t14.Text;
t4i.Text = t14i.Text;
t5.Text = t15.Text;
t6.Text = t16.Text;
t7.Text = t17.Text;
t8.Text = t18.Text;
t9.Text = t19.Text;
textBox1.Text = label49.Text;
}
private void comboBox1_SelectionChangeCommitted(object sender, EventArgs e)
{
string c1 = comboBox1.SelectedItem.ToString();
t1.Text = t1.Text +c1+",";
}
private void comboBox2_SelectionChangeCommitted_1(object sender, EventArgs e)
{
string c2 = comboBox2.SelectedItem.ToString();
t2.Text = t2.Text + c2 + ",";
}
private void comboBox3_SelectionChangeCommitted_1(object sender, EventArgs e)
{
string c3 = comboBox3.SelectedItem.ToString();
t3.Text = t3.Text + c3 + ",";
}
private void comboBox4_SelectedIndexChanged(object sender, EventArgs e)
{
string c4 = comboBox4.SelectedItem.ToString();
t4.Text = t4.Text + c4 + ",";
}
private void comboBox4i_SelectedIndexChanged(object sender, EventArgs e)
{
string c4i = comboBox4.SelectedItem.ToString();
t4i.Text = t4i.Text + c4i + ",";
}
private void comboBox5_SelectedIndexChanged(object sender, EventArgs e)
{
string c5 = comboBox5.SelectedItem.ToString();
t5.Text = t5.Text + c5 + ",";
}
private void comboBox6_SelectedIndexChanged(object sender, EventArgs e)
{
string c6 = comboBox6.SelectedItem.ToString();
t6.Text = t6.Text + c6 + ",";
}
private void comboBox7_SelectedIndexChanged(object sender, EventArgs e)
{
string c7 = comboBox7.SelectedItem.ToString();
t7.Text = t7.Text + c7 + ",";
}
private void comboBox8_SelectedIndexChanged(object sender, EventArgs e)
{
string c8 = comboBox8.SelectedItem.ToString();
t8.Text = t8.Text + c8 + ",";
}
private void comboBox9_SelectionChangeCommitted_1(object sender, EventArgs e)
{
string c9 = comboBox9.SelectedItem.ToString();
t9.Text = t9.Text + c9 + ",";
}
private void button1_Click_1(object sender, EventArgs e)
{
tabControl1.SelectedTab = tabPage3;
t1.Text = t21.Text;
t2.Text = t22.Text;
t3.Text = t23.Text;
t4.Text = t24.Text;
t4i.Text = t24i.Text;
t5.Text = t25.Text;
t6.Text = t26.Text;
t7.Text = t27.Text;
t8.Text = t28.Text;
t9.Text = t29.Text;
textBox1.Text = label47.Text;
}
private void button3_Click(object sender, EventArgs e)
{
if (t1.Text != "" && t2.Text != "" && t3.Text != "" && t4.Text != "" && t5.Text != "" && t6.Text != "" && t7.Text != "" && t8.Text != "" && t9.Text != "")
{
try
{
String con = "datasource = localhost; port=3306;username=root;password=brianfdes93";
MySqlConnection mycon = new MySqlConnection(con);
string query = "insert into cms.menu(o_id,wine,st_nonveg,st_veg,rice_nonveg,rice_veg,g_nonveg,g_veg,s_veg,s_nonveg,dessert) values('" + this.tid.Text + "','" + this.t1.Text + "','" + this.t2.Text + "','" + this.t3.Text + "','" + this.t4.Text + "','" + this.t4i.Text + "','" + this.t5.Text + "','" + this.t6.Text + "','" + this.t7.Text + "','" + this.t8.Text + "','" + this.t9.Text + "')";
MySqlCommand orderinsert = new MySqlCommand(query, mycon);
MySqlDataReader reader;
mycon.Open();
reader = orderinsert.ExecuteReader();
while (reader.Read())
{
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
try
{
String con1 = "datasource = localhost; port=3306;username=root;password=brianfdes93";
MySqlConnection mycon1 = new MySqlConnection(con1);
string query1 = "insert into cms.order(price_per_plate,total_amount) values('" + this.textBox1.Text + "','" + this.textBox2.Text+ "')";
MySqlCommand orderinsert1 = new MySqlCommand(query1, mycon1);
MySqlDataReader reader;
mycon1.Open();
reader = orderinsert1.ExecuteReader();
while (reader.Read())
{
}
MessageBox.Show("MENU PREFERENCE SAVED");
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
else
{
MessageBox.Show("please complete the form before submitting");
}
payment p = new payment();
this.Hide();
p.Show();
}
private void tabPage3_Enter(object sender, EventArgs e)
{
String con2 = "datasource = localhost; port=3306;username=root;password=brianfdes93";
MySqlConnection mycon2 = new MySqlConnection(con2);
string query2 = "select guest from cms.order where o_id='" + tid.Text + "'";
MySqlCommand orderinsert = new MySqlCommand(query2, mycon2);
string a = "1";
mycon2.Open();
// a = orderinsert.ExecuteScalar().ToString();
MySqlDataReader dr = orderinsert.ExecuteReader();
while (dr.Read())
{
a = dr.GetString(0);
}
string s = textBox1.Text;
int a1 = Convert.ToInt16(a);
int a2 = Convert.ToInt32(string.IsNullOrEmpty(textBox1.Text));
textBox2.Text = Convert.ToString(a1 * a2);
mycon2.Close();
}
}
}
我收到以下错误
输入字符串的格式不正确
我得到了a2的上述错误。
我该如何解决？ 还有另一种方式吗？
答案 0 :(得分：0)
Convert.ToInt16()用于将给定值转换为short（int16）而不是int（int32）。虽然它们是整数，但是short值应该分配给short（int16），而不是int（int32）。你需要使用Convert.ToInt32()方法将值转换为整数。
试试这个：
int a2 = Convert.ToInt32(textBox1.Text);
答案 1 :(得分：0)
如果textBox1.Text为空，则抛出此错误。 使用String.IsNullOrEmpty（textBox1.Text）检查textBox1.Text在转换为int16或int 32之前是否为null或空。如果它为null，则问题在于文本框本身。
答案 2 :(得分：0)
替换：
int a2 = Convert.ToInt32(string.IsNullOrEmpty(textBox1.Text));
with：
try
{
int a2 = Int.Parse(textBox1.Text);
}
catch (Exception ex)
{
Console.WriteLine("Failed to parse to int! " + ex.Message);
}
string.IsNullOrEmpty总是返回一个bool。