how to check only one checkbox from checkboxlist in c#?

Use SelectedIndexChanged event of checkedListBox1 .
Refer following code.

private void checkedListBox1_SelectedIndexChanged(object sender, EventArgs e)
       {
           int iSelectedIndex = checkedListBox1.SelectedIndex;
           if (iSelectedIndex == -1)
               return;
           for (int iIndex = 0; iIndex < checkedListBox1.Items.Count; iIndex++)
               checkedListBox1.SetItemCheckState(iIndex, CheckState.Unchecked);
           checkedListBox1.SetItemCheckState(iSelectedIndex, CheckState.Checked);
       }

use for loop like this

for(int i=0;i<chklist.items.count;i++)>
{
    if(chkList.GetItemChecked(i) == true)
    {
        //true
    }
}

Try this:

private void checkedListBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    int selNdx = checkedListBox1.SelectedIndex;

    foreach(int cbNdx in checkedListBox1.CheckedIndices)
    {
        if(cbNdx != selNdx)
        {
            checkedListBox1.SetItemChecked(cbNdx, false);
        }
    }
}

By using the 'CheckedIndices property of the CheckedListBox, you know which items are checked, and can test only those. Using this code, you don't have to deal with the fact that each Item in the CheckedListBox is Type 'object.

try this

jquery-make-checkboxes-act-like-radio-buttons[^]