Hashtable Issue

Hi I'm new to C#

This code allows for the word summary to be picked up from a combobox and the relevant XML documentation to be placed into a textbox. I can get this to work of I hard code a name eg Summary but cannot get the code to work if I want to ask if it "contains" a certain word.Can you help?

private void listBox7_SelectedIndexChanged(object sender, EventArgs e)
{

result = listBox7.Items[listBox7.SelectedIndex] as DocMember;

//Clear the text box of information.
textBox2.Clear();

if (comboBox2.Text != "")
{

if (comboBox2.Text == "summary")
// if(result.TagValues.Keys Contains (comboBox2.Text))
//if (comboBox2.Text Contains result.TagValues.Keys)
//if (result.TagValues.Keys Contains comboBox2.Text)
//if (result.TagValues.Keys) Contains comboBox2.Text
//if ((result.TagValues.Keys) Contains (comboBox2.Text))

{
string TagDetails = comboBox2.Text;
textBox2.Text = result.TagValues[comboBox2.Text].ToString();
}
else
{
MessageBox.Show("There are No TAGS present", "Warning", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
}
}