文本框中的自动递增数字

Question

如何在每次点击保存按钮时自动增加 textBox1 中的值（即 ID）？我的问题是 textBox1 中的值只会在我每次运行 winform 时增加。

例如，我运行 winform 并且 ID 的最后一个值为 2，textbox1 将生成数字 3，在我单击保存按钮后它不会生成下一个数字，而是只会在我关闭时增加表单并重新运行它。请帮助..

在表单加载中

  private void Form1_Load(object sender, EventArgs e)
    {
        int a;
        String path1 = "Data Source=LOCALHOST; Initial Catalog= ss; username=root; password=''";
        MySqlConnection con = new MySqlConnection(path1);
        con.Open();
        string query = "Select Max(ID) from inc";
        MySqlCommand cmd = new MySqlCommand(query, con);
        MySqlDataReader dr = cmd.ExecuteReader();
        if (dr.Read())
        {
            string val = dr[0].ToString();
            if (val == "")
            {
                textBox1.Text = "1";
            }
            else
            {
                a = Convert.ToInt32(dr[0].ToString());
                a = a + 1;
                textBox1.Text = a.ToString();
            }
        }
    }

在保存按钮中

 private void button1_Click(object sender, EventArgs e)
    {
        String path = "Data Source=LOCALHOST; Initial Catalog= ss; username=root; password=''";
        MySqlConnection sqlconn = new MySqlConnection(path); //communicator //constructors
        MySqlCommand sqlcomm = new MySqlCommand();
        MySqlDataReader sqldr;
        sqlconn.Open();
        sqlcomm.Connection = sqlconn;
        sqlcomm.CommandType = CommandType.Text;
        sqlcomm.CommandText = "Select * from inc where ID=" + textBox1.Text + "";

        sqldr = sqlcomm.ExecuteReader();
        sqldr.Read();

        if (sqldr.HasRows)
        {
            textBox3.Text = sqldr[0].ToString();

        }
        sqlconn.Close();


        if (textBox1.Text == textBox3.Text)
        {
            MessageBox.Show("ID already exists!");

        }

        else
        {
            String path1 = "Data Source=LOCALHOST; Initial Catalog= ss; username=root; password=''";
            MySqlConnection sqlconnn = new MySqlConnection(path1); //communicator //constructors
            MySqlCommand sqlcommm = new MySqlCommand();
            sqlconnn.Open();
            sqlcommm.Connection = sqlconnn;
            sqlcommm.CommandType = CommandType.Text;
            sqlcommm.CommandText = "INSERT INTO inc (ID,Lastname) VALUES ("+ textBox1.Text +", '" + textBox2.Text + "')";
            sqlcommm.ExecuteNonQuery();
            sqlconnn.Close();
            MessageBox.Show("RECORD SAVED!");
        }
    }

Answer 1

你只需要保存记录后更新textBox1.Text

...
sqlcommm.ExecuteNonQuery();
sqlconnn.Close();
MessageBox.Show("RECORD SAVED!");
//Update textBox1.Text
....

您必须为下次保存生成下一个值！

Answer 2

 private void Form1_Load(object sender, EventArgs e)
    {
        int a;
        String path1 = "Data Source=LOCALHOST; Initial Catalog= ss; username=root; password=''";
        MySqlConnection con = new MySqlConnection(path1);
        con.Open();
        string query = "Select Max(ID) from inc";
        MySqlCommand cmd = new MySqlCommand(query, con);
        MySqlDataReader dr = cmd.ExecuteReader();
        if (dr.Read())
        {
            string val = dr[0].ToString();
           setText(val );
        }
}


   private void button1_Click(object sender, EventArgs e)
    {
        String path = "Data Source=LOCALHOST; Initial Catalog= ss; username=root; password=''";
        MySqlConnection sqlconn = new MySqlConnection(path); //communicator //constructors
        MySqlCommand sqlcomm = new MySqlCommand();
        MySqlDataReader sqldr;
        sqlconn.Open();
        sqlcomm.Connection = sqlconn;
        sqlcomm.CommandType = CommandType.Text;
        sqlcomm.CommandText = "Select * from inc where ID=" + textBox1.Text + "";

        sqldr = sqlcomm.ExecuteReader();
        sqldr.Read();

        if (sqldr.HasRows)
        {
            textBox3.Text = sqldr[0].ToString();

        }
        sqlconn.Close();


        if (textBox1.Text == textBox3.Text)
        {
            MessageBox.Show("ID already exists!");

        }

        else
        {
            String path1 = "Data Source=LOCALHOST; Initial Catalog= ss; username=root; password=''";
            MySqlConnection sqlconnn = new MySqlConnection(path1); //communicator //constructors
            MySqlCommand sqlcommm = new MySqlCommand();
            sqlconnn.Open();
            sqlcommm.Connection = sqlconnn;
            sqlcommm.CommandType = CommandType.Text;
            sqlcommm.CommandText = "INSERT INTO inc (ID,Lastname) VALUES ("+ textBox1.Text +", '" + textBox2.Text + "')";
            sqlcommm.ExecuteNonQuery();
            sqlconnn.Close();
            MessageBox.Show("RECORD SAVED!");
           setText( textBox1.Text);
        }
    }

 private void setText(string newValue)
{

            if (newValue == "")
            {
                textBox1.Text = "1";
            }
            else
            {
                a = Convert.ToInt32(newValue);
                a = a + 1;
                textBox1.Text = a.ToString();
            }
}

您需要在每次成功保存时更新 ID。

Answer 3

试试这个

if (!Page.IsPostBack) {
ViewState["hereYourThingToIncrement"] = "1";
yourtxt.Text = ViewState["hereYourThingToIncrement"].ToString();
}

然后

protected void button(object sender, EventArgs e)
    {
int number=Convert.ToInt32(ViewState["hereYourThingToIncrement"]);
        ViewState["hereYourThingToIncrement"] = number+ 1;
        yourtxt.Text = ViewState["hereYourThingToIncrement"].ToString();

}