Why doesnt this work?

Question

foreach (DataRow dataRow in dt.Rows)
            {
                if (dataRow["Column1"].ToString().Contains(["ExampleString"])
                {

                    listBox1.Items.Add(dataRow["Column1"] + " " + dataRow["Column2"] + "  " + dataRow["Column3"] + " " + dataRow["Column4"]);

                }
            }


//the above code works perfectly and returns only the rows containing the "ExampleString"


// if i try to use a SelectedText value from a combobox as a string to replace the "ExampleString", (as shown below),the listbox populates with ALL of the rows, not just the ones with the "ExampleString".




string strFromCombobox = comboBox1.SelectedText;

foreach (DataRow dataRow in dt.Rows)
            {
                if (dataRow["Column1"].ToString().Contains(strFromCombobox)
                {

                    listBox1.Items.Add(dataRow["Column1"] + " " + dataRow["Column2"] + "  " + dataRow["Column3"] + " " + dataRow["Column4"]);

                }
            }