I'm trying to calculate an expression to SUM two ssrs textboxes but then I get the following error:
The Value expression for the textrun ‘Textbox343.Paragraphs[0].TextRuns[0]’ contains an error: [BC30456] 'textbox346' is not a member of 'Microsoft.ReportingServices.ReportProcessing.ReportObjectModel.ReportItems'.
The error message says that the control textbox346 can't be found. As you say that you try to calculate a SUM on this textbox, you probably want to do this in a group header or footer, but on that level, you can't access a report item (a textbox) on a lower level (a details row), because there can be many of them.
Also: Aggregate functions (like SUM) can't operate on expressions that refer to report items. The values in such expressions must depend just on the dataset. The amount of data can be controlled by grouping the tablix and using a scope for the function.
Therefore, if your textbox textbox346 (on the group details level) is bound to an expressions depending on just dataset fields, use that same expression in your SUM furmula in Textbox343 (in the group header or footer).
