c# - 不想在 C# 表单中插入空数据

问题描述

我制作了一个 SQL 数据库和一个 C# 表单。表格工作正常。当我从表单发送数据时，数据会正确插入到表中。但是我试过了，如果表格只有一个字段或者是空的，不要把数据发送到表中。我准备不允许表字段中的空数据。但除了主键之外，我可以为其他字段插入空数据。

这是我的主要表单代码。请改正

    private void Form1_Load(object sender, EventArgs e)
    {
        txtPassword.PasswordChar = '*';
        txtPasswordNew.PasswordChar = '*';
        gboxSignup.Visible = false;
    }

    private void btnOrSignup_Click(object sender, EventArgs e)
    {
        gboxSignup.Visible = true;

    }

    private void btnSignupNew_Click(object sender, EventArgs e)
    {
        if (txtFirstNameNew.Text != null && txtLasyNameNew.Text != null && txtUserNameNew.Text != null && txtPasswordNew.Text != null && txtEmailNew.Text != null)
        {
            try
            {
                Connect obj = new Connect();
                obj.conn.ConnectionString = obj.locate;
                obj.conn.Open();
                String insertUser = "insert into userTable values ('"+txtFirstNameNew.Text+ "','" +txtLasyNameNew.Text+ "','" +txtEmailNew.Text+ "','" +txtUserNameNew.Text+ "','" +txtPasswordNew.Text+"')";
                obj.cmd.Connection = obj.conn;
                obj.cmd.CommandText = insertUser;
                obj.cmd.ExecuteNonQuery();
                MessageBox.Show("Signup has been completed");
                gboxSignup.Visible = false;
                txtFirstNameNew.Text = "";
                txtLasyNameNew.Text = "";
                txtEmailNew.Text = "";
                txtPasswordNew.Text = "";
                txtUserNameNew.Text = "";



            }   
            catch (Exception ex)
            {
                MessageBox.Show("ERROR" + ex);
            }
        }
        else
        {
            MessageBox.Show("ERROR!!!  Fill in the All Fields");
        }
    }

    private void btnLogin_Click(object sender, EventArgs e)
    {
        if(txtUserName.Text != null && txtPassword.Text != null)
        {
            try
            {
                Connect obj = new Connect();
                obj.conn.ConnectionString = obj.locate;

                obj.conn.Open();
                SqlDataAdapter adapter = new SqlDataAdapter ("SELECT COUNT (*) FROM userTable where UserName = '" +txtUserName.Text+"' and Password = '"+txtPassword.Text+"' ", selectConnection: obj.conn );
                DataTable dt = new DataTable();
                adapter.Fill(dt);
                if (dt.Rows[0][0].ToString() == "1")
                {
                    frmWelcome meLoad = new frmWelcome();
                    meLoad.Visible = true;
                    this.Hide();
                    MessageBox.Show("Sucessfully Login");
                }
                else
                {
                    MessageBox.Show("User Name Or Password is incorrect - Try it");
                }
                obj.conn.Close();

            }
            catch(Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
        else
        {
            MessageBox.Show("No Empty Field Allowed");
        }
    }
}

}

这是连接类代码

class Connect
{
    public SqlConnection conn = new SqlConnection();
    public SqlCommand cmd = new SqlCommand();
    public string locate = @"Data Source=(LocalDB)\MSSQLLocalDB;AttachDbFilename='J:\D Drive\Excersize\C#\Windowsform\WindowsFormsApp1\UserDB.mdf';Integrated Security=True";

}

这是我的表格设计（userTable）

这是在插入数据之后。

这是我的表单设计

插入可以空数据

插入数据尝试无主键

标签： c#sqlformsnull

c# - 不想在 C# 表单中插入空数据

问题描述

解决方案

推荐阅读