suspecious query parameters

Hi:
My website sends error reports to me once there is any error occur, today, I got 3 suspecious errors:
/UserProfile.aspx?UserName=jam851+or+1=@@version
/UserProfile.aspx?UserName=jam851'+or+1=@@version
/UserProfile.aspx?UserName=jam851+or+1=@@version--
Detailed error is:
"Message: Exception of type 'System.Web.HttpUnhandledException' was thrown.
Source: System.Web
Method: Boolean HandleError(System.Exception)
Stack Trace:
at System.Web.UI.Page.HandleError(Exception e) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest() at System.Web.UI.Page.ProcessRequestW ...