InfoPath Dev

Hello everyone,

 I have been trying for days now, to figure out but nothing id working :(

i am writing some code on changed event  to check the content of one of my fields in infopath, if the field contains anything (int in this case), then I display a message that the field must be blank and then I want to delete that content. I gues I have to add the xsi:nil = "true" attribute?! which I do not know how....I tried SetValue("") but that is considered a string and since my field is an int, it does not like. Can anyone PLEASE help me on how to add this attribute or if there is anyother way to make this field blank. I will GREATLY appreciate it. Thanks.

here is my attempted code:

TOTAL_LENGTH_1MM = TOTAL_LENGTH_1MM.SelectSingleNode("/my:myFFIM_base_table/my:Species_Records/my:SpeciesGroup/my:GROUP_1MM/my:GROUP_1MM_sub/my:TOTAL_LENGTH_1MM", NamespaceManager);

MessageBox.Show("NOSP (No fish collected) was indicated. Length should be BLANK.");

TOTAL_LENGTH_1MM.SetValue(string.Empty);

TOTAL_LENGTH_1MM.CreateAttribute("xsi", "nil", System.Xml.Schema.XmlSchema.InstanceNamespace, "true");

Edit: Changed LookupNamespace() function to constant reference - same behavior but this is a better practice.

Thank you for the quick response Jimmy. I added TOTAL_LENGTH_1MM.CreateAttribute("xsi", "nil", NamespaceManager.LookupNamespace("xsi"), "true"); to my code, but now I am getting this message

  System.InvalidOperationException was unhandled by user code
  Message="Schema validation found non-data type errors."
  Source="Microsoft.Office.InfoPath.Client.Internal.Host.Interop"

any idea what this is about ?? (I tried 'googling' it, but I did not find anything useful). Thanks again!

 Did you remove the line to make the node blank? It has to be blank before you add the nil attribute.

that was it. THANK YOU very much!!! it WORKS!!!

 Please please i need help, this code doesn't work properly, i don't know how to write code for xsi:

XPathNavigator nav = MainDataSource.CreateNavigator()

nav.SelectSingleNode("//my:NewjoueurDatedenaissance", NamespaceManager).SetValue(string.Empty);

nav.SelectSingleNode("//my:NewjoueurDatedenaissance", NamespaceManager).CreateAttribute("xsi", "nil", NamespaceManager.LookupNamespace("xsi"), "true");