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。