To fix the previous error, I needed to set the dataset to rebind after each postback.

But now I am getting a script error each time on the second attempt to expand a parent row. The first expansion attempt always works, on any row. But the second expansion attempt (parent row) always fails with the error:

"Microsoft JScript runtime error: Sys.ArgumentException: Cannot deserialize. The data does not correspond to valid JSON. Parameter name: data"

Thanks. I've seen that sample.

I've bound the dataset to the grid, but I'm getting an error alert when I try to expand a parent row:

"Runtime Exception: No child grid script descriptors are available!"

I'm manually setting the primary key on each table in the dataset. I'm then setting the relations in the dataset. The grid is set to autogenerate columns and bands. InitialDataBindDepth is set to 0. Is there something else I'm missing?