The CompareValidator control compares the value of one control to another, or to an explicit value in the control's ValueToCompare property. CompareValidator uses three key properties to perform its validation. ControlToValidate and ControlToCompare contain the values to compare. Operator defines the type of comparison to perform, for example, Equal, Not Equal, Greater than, Less than, DataType and others. CompareValidator performs the validation by evaluating these properties as an expression.
When the type of value being compared is not a string, you have to specify the Type property as one of the following: