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How do you appropriately setup a plugin data source to allow for null values (in .NET - C# preferred)?

I'm currently setting up a field using:

field.Type_2 = esriFieldType.esriFieldTypeSingle;
field.IsNullable_2 = true;
field.Name_2 = "Foo";

Then, later, during the cursor's QueryValues call, I'm trying to set a null value via:

// Given: public int QueryValues(IRowBuffer row)
row.Value[i] = null;

However, the value always maps through as 0, not null. How do you properly setup the data source in a plugin data source to allow for a null value?

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up vote 7 down vote accepted

Have you tried setting DBNull.Value instead of null?

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Thanks! I hadn't tried that, as their examples show setting it to null directly - but this does actually work (where the other doesn't). – Reed Copsey Feb 21 '11 at 23:27
The documentation is sometimes null and void :) Do you have a link to this example? – Kirk Kuykendall Feb 22 '11 at 16:39
I believe most of the .NET samples were converted from VB rather badly, perhaps semi-automatically I guess. In .NET COM interop, the VT_NULL (Null in VB/VBA) variant, which is used for denoting null values, maps directly to DBNull in .NET. – Petr Krebs Feb 22 '11 at 19:15

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