如何更改组合框的默认值

Question

我正试图使基于项目选择抛出组合框的SQL语句。我想有默认项目选择作为ID，但现在它返回NULL。我做错了什么?

private void Win_Shown(object sender, EventArgs e)
{
myBox.SelectedValue = "ID";
myBox.SelectedText = "ID";
myBox.SelectedItem = "ID";
myBox.Items.Add("ID");
myBox.Items.Add("Name");
myBox.Items.Add("Surname");
myBox.Items.Add("Mobile"); 
}

Then in for SQL语句

MySQL.DisplayAndSearch("SELECT * FROM Data WHERE " + this.myBox.SelectedItem.ToString() + " LIKE '%" + txt_Search.Text + "%'", dataGridView1);

谢谢你的帮助:)

Answer 1

在插入前选择条目:

private void Win_Shown(object sender, EventArgs e)
{
// first, add the items   
myBox.Items.Add("ID");
myBox.Items.Add("Name");
myBox.Items.Add("Surname");
myBox.Items.Add("Mobile"); 
// now select it
myBox.SelectedItem = "ID";
}

Answer 2

你试过了吗?

private void Win_Shown(object sender, EventArgs e)
{

myBox.Items.Add("ID");
myBox.Items.Add("Name");
myBox.Items.Add("Surname");
myBox.Items.Add("Mobile"); 
// now select it
myBox.SelectedIndex = myBox.FindString("Mobile");//id..etc
}