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Q&A How to change the color of a cell to a user defined value while keeping its existing style using NPOI from F#?

The answer provided in the How to set the cell color to a user defined value using NPOI from F#? thread solves the problem of how to set the right properties using F#, but it uses a new ICellStyle ...

1 answer · posted 11mo ago by toraritte‭ · last activity 11mo ago by toraritte‭

Question f# excel NPOI

#2: Post edited by

toraritte‭ · 2024-01-11T16:08:13Z (11 months ago)

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The answer provided in the [How to set the cell color to a user defined value using NPOI from F#?](https://stackoverflow.com/questions/77701061/how-set-the-cell-color-to-a-user-defined-value-using-npoi-from-f) thread solves the problem of how to set the right properties using F#, but it uses a new `ICellStyle` object and overwrites the existing style with it.
Re-writing the function (see below) to setting the existing cell's styling properties directly has a side effect of painting most of the cells in the sheet with the same color.
```
let changeCellColorDirectly (cell: ICell) (rgb: byte array) =
let xssfCell = cell :?> NPOI.XSSF.UserModel.XSSFCell
match xssfCell.CellStyle with
| :? NPOI.XSSF.UserModel.XSSFCellStyle as xssfCellStyle ->
let color = new NPOI.XSSF.UserModel.XSSFColor(rgb)
xssfCellStyle.FillForegroundXSSFColor <- color
xssfCellStyle.FillPattern <- NPOI.SS.UserModel.FillPattern.SolidForeground
| _ -> failwith "'newCellStyle' cannot be cast to XSSFCellStyle"
```
I presume that same-styled cells share the same `ICellStyle` object, so I tried to solve this with `ICellStyle`'s `CloneStyleFrom` method (see below), but the result was the same.
```
let changeCellColorByCloning (cell: ICell) (rgb: byte array) =
let xssfCell: NPOI.XSSF.UserModel.XSSFCell = cell :?> NPOI.XSSF.UserModel.XSSFCell
let newCellStyle: NPOI.SS.UserModel.ICellStyle = xssfCell.Sheet.Workbook.CreateCellStyle()
newCellStyle.CloneStyleFrom(xssfCell.CellStyle)
match newCellStyle with
| :? NPOI.XSSF.UserModel.XSSFCellStyle as xssfCellStyle ->
let color = new NPOI.XSSF.UserModel.XSSFColor(rgb)
xssfCellStyle.FillForegroundXSSFColor <- color
xssfCellStyle.FillPattern <- NPOI.SS.UserModel.FillPattern.SolidForeground
| _ -> failwith "'newCellStyle' cannot be cast to XSSFCellStyle"
xssfCell.CellStyle <- newCellStyle
```

The answer provided in the [How to set the cell color to a user defined value using NPOI from F#?](https://software.codidact.com/posts/290555) thread solves the problem of how to set the right properties using F#, but it uses a new `ICellStyle` object and overwrites the existing style with it.
Re-writing the function (see below) to setting the existing cell's styling properties directly has a side effect of painting most of the cells in the sheet with the same color.
```
let changeCellColorDirectly (cell: ICell) (rgb: byte array) =
let xssfCell = cell :?> NPOI.XSSF.UserModel.XSSFCell
match xssfCell.CellStyle with
| :? NPOI.XSSF.UserModel.XSSFCellStyle as xssfCellStyle ->
let color = new NPOI.XSSF.UserModel.XSSFColor(rgb)
xssfCellStyle.FillForegroundXSSFColor <- color
xssfCellStyle.FillPattern <- NPOI.SS.UserModel.FillPattern.SolidForeground
| _ -> failwith "'newCellStyle' cannot be cast to XSSFCellStyle"
```
I presume that same-styled cells share the same `ICellStyle` object, so I tried to solve this with `ICellStyle`'s `CloneStyleFrom` method (see below), but the result was the same.
```
let changeCellColorByCloning (cell: ICell) (rgb: byte array) =
let xssfCell: NPOI.XSSF.UserModel.XSSFCell = cell :?> NPOI.XSSF.UserModel.XSSFCell
let newCellStyle: NPOI.SS.UserModel.ICellStyle = xssfCell.Sheet.Workbook.CreateCellStyle()
newCellStyle.CloneStyleFrom(xssfCell.CellStyle)
match newCellStyle with
| :? NPOI.XSSF.UserModel.XSSFCellStyle as xssfCellStyle ->
let color = new NPOI.XSSF.UserModel.XSSFColor(rgb)
xssfCellStyle.FillForegroundXSSFColor <- color
xssfCellStyle.FillPattern <- NPOI.SS.UserModel.FillPattern.SolidForeground
| _ -> failwith "'newCellStyle' cannot be cast to XSSFCellStyle"
xssfCell.CellStyle <- newCellStyle
```

#1: Initial revision by

toraritte‭ · 2024-01-11T16:06:00Z (11 months ago)

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How to change the color of a cell to a user defined value while keeping its existing style using NPOI from F#?

The answer provided in the [How to set the cell color to a user defined value using NPOI from F#?](https://stackoverflow.com/questions/77701061/how-set-the-cell-color-to-a-user-defined-value-using-npoi-from-f) thread solves the problem of how to set the right properties using F#, but it uses a new `ICellStyle` object and overwrites the existing style with it.

Re-writing the function (see below) to setting the existing cell's styling properties directly has a side effect of painting most of the cells in the sheet with the same color.

```
let changeCellColorDirectly (cell: ICell) (rgb: byte array) =
    let xssfCell = cell :?> NPOI.XSSF.UserModel.XSSFCell
    match xssfCell.CellStyle with
    | :? NPOI.XSSF.UserModel.XSSFCellStyle as xssfCellStyle ->
        let color = new NPOI.XSSF.UserModel.XSSFColor(rgb)
        xssfCellStyle.FillForegroundXSSFColor <- color
        xssfCellStyle.FillPattern <- NPOI.SS.UserModel.FillPattern.SolidForeground
    | _ -> failwith "'newCellStyle' cannot be cast to XSSFCellStyle"
```

I presume that same-styled cells share the same `ICellStyle` object, so I tried to solve this with `ICellStyle`'s `CloneStyleFrom` method (see below), but the result was the same.

```
let changeCellColorByCloning (cell: ICell) (rgb: byte array) =
    let xssfCell: NPOI.XSSF.UserModel.XSSFCell = cell :?> NPOI.XSSF.UserModel.XSSFCell
    let newCellStyle: NPOI.SS.UserModel.ICellStyle = xssfCell.Sheet.Workbook.CreateCellStyle()
    newCellStyle.CloneStyleFrom(xssfCell.CellStyle)
    match newCellStyle with
    | :? NPOI.XSSF.UserModel.XSSFCellStyle as xssfCellStyle ->
        let color = new NPOI.XSSF.UserModel.XSSFColor(rgb)
        xssfCellStyle.FillForegroundXSSFColor <- color
        xssfCellStyle.FillPattern <- NPOI.SS.UserModel.FillPattern.SolidForeground
    | _ -> failwith "'newCellStyle' cannot be cast to XSSFCellStyle"
    xssfCell.CellStyle <- newCellStyle
```

f# excel NPOI

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