C#学习笔记五-HashTable

 学到集合中的HashTable的时候，做一个题目总是有错误，今天总算解决了，好爽。虽然只是小小问题一个。

 

当我添加信息时，把姓名加到右边的lstBox里，并且以姓名做为键，其他三项保存在一个Employee类中，以这个类的实例作为值将这三项数据保存在一个HashTable中，在"修改"和"删除"的时候，ListBox中的相应信息和HashTable中相应信息都会改动。用来存储信息的类Employee:    class Employee    {        private string _empNo;        private string _Name;        private string _Department;        private float _Salary;

        public Employee(string No, string EName, string Depart, float Salary)        {            this._empNo = No;            this._Name = EName;            this._Department = Depart;            this._Salary = Salary;        }        public string EmpNo         {            get            {                return _empNo;             }        }        public string Name        {            get            {                return this._Name;            }        }        public string Department        {            get            {                return _Department;            }        }        public float Salray        {            get            {                return this._Salary;            }        }    }当ListBox中选择项改变的时候的事件：        private void lstShow_SelectedIndexChanged(object sender, EventArgs e)        {            try            {                IDictionaryEnumerator myhash = _HashCode.GetEnumerator();                if (this.lstShow.SelectedIndex == -1)                {                    this.txtempNo.Text = "";                    this.txtName.Text = "";                    this.txtDepart.Text = "";                    this.txtSalary.Text = "";                }                else                {                    while (myhash.MoveNext())                    {                        Employee emp = (Employee)_HashCode[myhash.Key];                        if (lstShow.SelectedItem.ToString() == emp.Name)                        {                            this.txtempNo.Text = emp.EmpNo;                            this.txtName.Text = emp.Name;                            this.txtDepart.Text = emp.Department;                            this.txtSalary.Text = emp.Salray.ToString();                        }

                    }                }

            }            catch (InvalidOperationException i)            {                MessageBox.Show(i.Message);            }

        }

我的“添加”按钮事件：        private void btnAdd_Click(object sender, EventArgs e)        {            if (this.txtempNo.Text == "" || this.txtempNo.Text == null)            {                MessageBox.Show("请输入职工编号！");                this.txtempNo.Focus();                return;            }            else if (this.txtName.Text == "" || this.txtName.Text == null)            {                MessageBox.Show("请输入姓名！");                this.txtName.Focus();                return;            }            else if (this.txtDepart.Text == "" || this.txtDepart.Text == null)            {                MessageBox.Show("请输入部门！");                this.txtDepart.Focus();                return;            }            else if (this.txtSalary.Text == ""|| float.Parse(this.txtSalary.Text) < 0)            {                MessageBox.Show("未输入工资或工资小于０！");                this.txtSalary.Focus();                return;            }            else            {                try                {                    this._HashCode.Add(this.txtName.Text, new Employee(this.txtempNo.Text, this.txtName.Text, this.txtDepart.Text, float.Parse(this.txtSalary.Text)));                    this.lstShow.Items.Add(this.txtName.Text);                }                catch (Exception ne)                {                    MessageBox.Show(ne.Message);                }                            }        }

“修改”按钮的事件：private void button1_Click(object sender, EventArgs e)        {            if (lstShow.SelectedIndex == -1)            {                MessageBox.Show("请选择要修改的信息！");                return;            }            try            {                int index = lstShow.SelectedIndex;                this._HashCode.Remove(lstShow.SelectedItem.ToString());                lstShow.Items.RemoveAt(index);                lstShow.Items.Insert(index, this.txtName.Text);                this._HashCode.Add(name, new Employee(this.txtempNo.Text,this.txtName.Text,this.txtDepart.Text,float.Parse(this.txtSalary.Text)));                            }            catch (Exception ex)            {                MessageBox.Show(ex.Message);            }        }

“删除”按钮的事件：private void btnDelete_Click(object sender, EventArgs e)        {            IDictionaryEnumerator myhash = _HashCode.GetEnumerator();            if (lstShow.SelectedIndex == -1)            {                MessageBox.Show("请选择要删除的信息！");                return;            }            try            {                while (myhash.MoveNext())                {                    Employee employee = (Employee)_HashCode[myhash.Key];                    if (lstShow.SelectedItem.ToString() == employee.Name)                    {                        this._HashCode.Remove(lstShow.SelectedItem.ToString());                        lstShow.Items.RemoveAt(lstShow.SelectedIndex);                    }                }            }            catch            {                MessageBox.Show("成功删除。");            }        }

“关闭”按钮的事件：private void btnClose_Click(object sender, EventArgs e)        {            this.Close();        }

我要说的就是“修改”按钮的事件有错误：     先把选定的从listBox 和HashTable中删除，后面我又从TextBox中读取修改后的数据，而这时候不管是在listBox和HashTable中都不存在这条数据了。

在删除之前把修改的数据保存起来就可以解决：“修改”按钮事件改为：        private void button1_Click(object sender, EventArgs e)        {            string number;            string name;            string department;            float salary;            if (lstShow.SelectedIndex == -1)            {                MessageBox.Show("请选择要修改的信息！");                return;            }            try            {                number = this.txtempNo.Text;                name = this.txtName.Text;                department = this.txtDepart.Text;                salary = float.Parse(this.txtSalary.Text);                int index = lstShow.SelectedIndex;                this._HashCode.Remove(lstShow.SelectedItem.ToString());                lstShow.Items.RemoveAt(index);                lstShow.Items.Insert(index, name);                this._HashCode.Add(name, new Employee(number, name, department, salary));            }            catch (Exception ex)            {                MessageBox.Show(ex.Message);            }        }

还有一个限制工资文本框只能输入数字的键盘事件：        private void txtSalary_KeyPress(object sender, KeyPressEventArgs e)        {            if (!char.IsNumber(e.KeyChar) && e.KeyChar != (char)8 && e.KeyChar != (char)46)                e.Handled = true;        }

感觉这种方法很笨，你有好点的方法吗？有的话不要吝啬啦！这样做的话，保存在HashTable中的数据存储的顺序就改变了。