这段程序中,若要判断DateTime为空时,弹出"请输入日期格式"!

Question

private void button9_Click(object sender, EventArgs e)
        {
            string BookID = textBox21.Text.Trim();
            string ISBN = textBox22.Text.Trim();
            string BookName = textBox23.Text.Trim();
            string Authar = textBox24.Text.Trim();
            DateTime PulishDate = Convert.ToDateTime(textBox25.Text.Trim());
            string Pulisher = textBox26.Text.Trim();
            //decimal Price =decimal.Parse(textBox1.Text.Trim());
            bool IsCancel = false;
            string BookTypeID = comboBox1.SelectedValue.ToString().Trim();
            if (BookID == "")
            {
                MessageBox.Show("图书编号不能为空!");
                return;
            }
            //if (winLogin.HasThisBook(BookID))
            //{
            //    MessageBox.Show("该图书编号已存在，不能插入相同的图书编号!");
            //    return;
            //}  
            if (ISBN == "")
            {
                MessageBox.Show("请输入ISBN号!");
                return;
            }
            if (BookName == "")
            {
                MessageBox.Show("请输入图书编号!");
                return;
            }
            if (Pulisher == "")
            {
                MessageBox.Show("请输入图书出版社!");
                return;
            }
            if (comboBox1.SelectedIndex ==-1)
            {
                MessageBox.Show("请选择图书类型!");
                return;
            }
            try
            {
                Price = decimal.Parse(textBox1.Text.Trim());
            }
            catch
            {
                MessageBox.Show("请输入正确的金额格式!");
                return;
            }
            if (radioButton11.Checked)
            {
                if (winLogin.InsertNewBook(BookID, ISBN, BookName, Authar, PulishDate, Pulisher, Price, IsCancel, BookTypeID))
                {
                    MessageBox.Show("新书入库成功！");
                    dataGridView1.DataSource = winLogin.GetBookInfo(BookID).Tables[0];
                }
            }
            else
            {
                MessageBox.Show("新书入库失败！");
            }
        }

Answer 1

//DateTime PulishDate = Convert.ToDateTime(textBox25.Text.Trim());
DateTime PulishDate;
if(textBox25.Text.Trim().Length == 0)
{
     MessageBox.Show("请输入日期格式!");
}
else
{
     try
     {
           PulishDate = Convert.ToDateTime(textBox25.Text.Trim());
     }
     catch
     {
           MessageBox.Show("请输入正确的日期格式!");
     }
}

Answer 2

DateTime PulishDate = Convert.ToDateTime(textBox25.Text.Trim());
可能抛异常了，做个try catch就行了
或者判断textBox25.Text.Trim()是不是为""

Answer 3

3l正解也可以是if(textBox25.Text.Trim()== string.empty)
{
     MessageBox.Show("请输入日期格式!");
}
else
{
     try
     {
           PulishDate = Convert.ToDateTime(textBox25.Text.Trim());
     }
     catch
     {
           MessageBox.Show("请输入正确的日期格式!");
     }
}

Answer 4

if(textBox25.Text.Trim()== string.empty) 
{ 
    MessageBox.Show("请输入日期格式!"); 
} 
else 
{ 
if(!DateTime.TryParse(textBox25.Text.Trim(),out  PulishDate ))
{
MessageBox.Show("请输入正确的日期格式!"); 
} 
} 

Answer 5

//估计是这个意思
//DateTime PulishDate = Convert.ToDateTime(textBox25.Text.Trim());
DateTime PulishDate;
if(textBox25.Text.Trim().Length == 0)
{
     ErrorProvider errorProvider1=new ErrorProvider();
     errorProvider1.SetError(textBox25,"请输入日期格式!");     
}
else
{
     try
     {
           PulishDate = Convert.ToDateTime(textBox25.Text.Trim());
     }
     catch
     {
           MessageBox.Show("请输入正确的日期格式!");
     }
}

Answer 6

日期请不要用TextBox ，请用DateTimePicker 控件。

Answer 7

 DateTime PulishDate = Convert.ToDateTime(textBox25.Text.Trim());
这你要判断不为空和是否是时间格式以后在强制转换