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Gets or sets the data validation input message.
The input message is displayed when the user selects a cell in the validated range if input messages are enabled for the validation.
string InputMessage { get; set; }
Property InputMessage As String
IValidation validation = worksheet.Range["A1"].Validation;
validation.Add(ValidationType.Whole, ValidationAlertStyle.Stop, ValidationOperator.Between, 1, 10);
validation.InputMessage = "Enter a whole number from 1 to 10.";
string inputMessage = validation.InputMessage;