<asp:LinkButton ID="lnkBtn" CommandName ="sendLink" runat="server"
OnClientClick='javascript:AddToDatabase(<%# Eval("myUrl") %>)'
CommandArgument='<%# Eval("myUrl") %>' Text='<%# Eval("myUrl") %>'>
</asp:LinkButton>
Edit 1
change OnClientClick as follows
OnClientClick='<%# Eval("myUrl", "javascript:AddToDatabase({0});") %>'
combining both
<asp:LinkButton ID="lnkBtn" CommandName ="sendLink" runat="server"
OnClientClick='<%# Eval("myUrl", "javascript:AddToDatabase({0});") %>'
CommandArgument='<%# Eval("myUrl") %>' Text='<%# Eval("myUrl") %>'>
</asp:LinkButton>
References
Passing Eval parameter to a JavaScript function from ASPX file
Edit 2
Here is another link
Passing variables to javascript in onclientclick
passing a rowindex from gridview item click to javascript function
Edit 3
The one which helped answerer by the @moiz
<asp:LinkButton ID="lnkBtn" CommandName ="sendLink" runat="server"
OnClientClick='<%# Eval("myUrl", "javascript:AddToDatabase('{0}');") %>'
CommandArgument='<%# Eval("myUrl") %>' Text='<%# Eval("myUrl") %>'>
'<%# Eval("myUrl") %>'
</asp:LinkButton>