String确实包含isnullorwhitespace的定义

Question

请帮我系统。我不知道isnullorwhitespace：

的问题

我的错误是：

  

“string确实包含isnullorwhitespace的定义”

isnullorwhitespace的其他选择是什么？

private void btnAdd_Click(object sender, EventArgs e)
{
    int age = int.Parse(txtage.Text);
    if (string.IsNullOrWhiteSpace(txtfname.Text))
    {
        MessageBox.Show("Please input your firstname!");
    }
    else if(string.IsNullOrWhiteSpace(txtlname.Text))
    {
        MessageBox.Show("Please input your lastname!");
    }
    else if(string.IsNullOrWhiteSpace(cbgender.SelectedItem.ToString()))
    {
        MessageBox.Show("Please specify your gender!");
    }
    else if(string.IsNullOrWhiteSpace(txtage.Text) || age <= 0 )
    {
        MessageBox.Show("Please assign your birthdate to know your age!");
    }
    else if(string.IsNullOrWhiteSpace(txtcontact.Text))
    {
        MessageBox.Show("Please input your contact number!");
    }
    else if(string.IsNullOrWhiteSpace(txtAddress.Text))
    {
        MessageBox.Show("Please input your address!");
    }
    else if(string.IsNullOrWhiteSpace(txtUsername.Text))
    {
        MessageBox.Show("Please input your username!");
    }   
    else if(string.IsNullOrWhiteSpace(txtPass.Text))
    {
        MessageBox.Show("Please input your password!");
    }
    else if(string.IsNullOrWhiteSpace(cbxQuest.SelectedItem.ToString()))
    {
        MessageBox.Show("Please specify your secret question!");
    }
    else if(string.IsNullOrWhiteSpace(txtAsnwer.Text))
    {
        MessageBox.Show("Please input your answer!");
    }
    else 
    {

        //Insert 7
        ui.fname = txtfname.Text;
        ui.lname = txtlname.Text;
        ui.gender = cbgender.SelectedItem.ToString();
        ui.age = int.Parse(txtage.Text);
        ui.bdate = dtpBdate.Value;
        ui.contactNo = txtcontact.Text;
        ui.Adress = txtAddress.Text;
        //Insert 4
        us.username = txtUsername.Text;
        us.passwordHash = txtPass.Text;
        us.secretQuestion = cbxQuest.SelectedItem.ToString();
        us.secretAnswer = txtAsnwer.Text;

        StoredProcedure.Insert(ui, us);
        dgData.DataSource = StoredProcedure.View();
        Clear();
    }

Answer 1

String.IsNullOrWhiteSpace已在.NET 4中引入。如果您不是针对.NET 4，那么您可以轻松编写自己的：

//options has information like hostname, path, etc.
var req = https.request(options, function(res) {
  res.setEncoding('utf8');
  res.on('data', function (response) {
    console.log(response); //this is the JSON that you're seeing
    item = JSON.parse(response);
    console.log(item.kind);
  });
});

可以像这样使用：

public static class StringExtensions
{
    public static bool IsNullOrWhiteSpace(string value)
    {
        if (value != null)
        {
            for (int i = 0; i < value.Length; i++)
            {
                if (!char.IsWhiteSpace(value[i]))
                {
                    return false;
                }
            }
        }
        return true;
    }
}