Question: I have stored procedure which returns around 100 rows. One column is Category. 

In SSRS, I've created DataSet related to that stored procedure. On Report body I have Tablix, which I relate to DataSet.

Now, I have additional parameter, called FilterColumn, which consist all different categories from dataset, plus one row called "All products". 

How to filter tablix based on that parameter to show me whether products from specific categories or all products?

Answer: 
I have created some solution and worked for me:

![enter image description here](https://i.stack.imgur.com/2qamj.png)

In `Expression` field, I put first expression: 

```
1.  Iif(Parameters!FilterColumn.Value = "All", 1, Fields!Category.Value)

```

In `Value` field, I put second expression:

```
2.  Iif(Parameters!FilterColumn.Value = "All", 1, Parameters!FilterColumn.Value)

```

So, when I choose "All" value in parameter, then first expression will result 1, and second expression will result 1, and i have `1 = 1` which is true for all rows, and I got all rows in table.

When I choose specific category from parameter, then in first expression result will be `Fields!Category.Value` and in second expression will be `Parameters!FilterColumn.Value`. Simple, I got `Fields!Category.Value = Parameters!FilterColumn.Value`, or just give me rows where category is that choosen in parameter.
Pass the Additional Parameter to your store procedure, so you send data that is already sorted to your report. This will avoid multiple Tablix created depending on your parameter selection.