Added new kb article changing-date-format-exported-excel-blazor-grid (#670)

* Added new kb article changing-date-format-exported-excel-blazor-grid

* polished

---------

Co-authored-by: KB Bot <kb-bot@telerik.com>
Co-authored-by: Desislava Yordanova <dyordano@progress.com>

Author: 3 people

knowledge-base/changing-date-format-exported-excel-blazor-grid.md

@@ -0,0 +1,70 @@
+---
+title: Changing Date Format of Exported Excel File from UI Grid components
+description: Learn how to change the Date format in exported Excel files generated by data from a Grid component using Telerik Document Processing RadSpreadProcessing.
+type: how-to
+page_title: Formatting Date Columns in Exported Excel Files from Blazor Grid
+meta_title: Formatting Date Columns in Exported Excel Files from Blazor Grid
+slug: changing-date-format-exported-excel-blazor-grid
+tags: spread,processing, telerik, document, grid, excel, date, format
+res_type: kb
+ticketid: 1702751
+---
+
+## Environment
+
+| Version | Product | Author | 
+| ---- | ---- | ---- | 
+| 2025.3.806| RadSpreadProcessing |[Desislava Yordanova](https://www.telerik.com/blogs/author/desislava-yordanova)| 
+
+## Description
+
+Learn how to apply a custom date format (e.g., "yyyy-MM-dd") to the relevant columns in the exported Excel file generated from UI Grid components offered by the Telerik family.
+
+<img style="border: 1px solid gray;" src="images/changing-date-format-exported-excel-blazor-grid.png" /> 
+
+## Solution
+
+To change the date format in the exported Excel file, use [RadSpreadProcessing]({%slug radspreadprocessing-overview%}) to modify the exported stream before saving the file.
+
+Follow these steps:
+
+1. Export the grid data to a `MemoryStream`.
+2. Load the exported stream into a workbook using the [XlsxFormatProvider]({%slug radspreadprocessing-formats-and-conversion-xlsx-xlsxformatprovider%}).
+3. Apply a custom [date format]({%slug radspreadprocessing-features-format-codes%}#date-and-time-formatting) to the desired column in the workbook.
+4. Save the modified workbook to a file.
+
+Here is an example implementation:
+
+```csharp
+static void Main(string[] args)
+{
+    // Step 1: Export the grid data to a MemoryStream
+    var exportedExcelStream = new MemoryStream(File.ReadAllBytes("exported-grid.xlsx"));
+
+    // Step 2: Load the exported stream into a workbook
+    XlsxFormatProvider formatProvider = new XlsxFormatProvider();
+    Workbook workbook = formatProvider.Import(exportedExcelStream, TimeSpan.FromSeconds(10));
+
+    // Step 3: Apply date format to the desired column (e.g., column index 2 for Dates)
+    CellValueFormat dateFormat = new CellValueFormat("yyyy-MM-dd");
+    ColumnSelection dateColumn = workbook.Worksheets[0].Columns[2]; // Update index as needed
+    dateColumn.SetFormat(dateFormat);
+
+    // Step 4: Save the modified workbook to a file
+    string outputFilePath = "formatted.xlsx";
+    File.WriteAllBytes(outputFilePath, formatProvider.Export(workbook, TimeSpan.FromSeconds(10)));
+    Process.Start(new ProcessStartInfo() { FileName = outputFilePath, UseShellExecute = true });
+}
+```
+
+### Explanation
+
+- **Step 1:** Reads the exported Excel file into a `MemoryStream`.
+- **Step 2:** Utilizes `XlsxFormatProvider` to parse the stream into a `Workbook` object for manipulation.
+- **Step 3:** Sets a custom date format for the targeted column using `SetFormat`.
+- **Step 4:** Saves the updated workbook and opens the file using the default application.
+
+## See Also
+
+- [XlsxFormatProvider]({%slug radspreadprocessing-formats-and-conversion-xlsx-xlsxformatprovider%})
+- [Date and Time Formatting]({%slug radspreadprocessing-features-format-codes%}#date-and-time-formatting) 

knowledge-base/images/changing-date-format-exported-excel-blazor-grid.png

@@ -418,3 +418,4 @@ The regional currency settings determine the position of the currency symbol rel
 ## See Also
 
 * [Number Formatting]({%slug radspreadprocessing-features-number-formats%})
+* [Changing Date Format of Exported Excel File from UI Grid components]({%slug changing-date-format-exported-excel-blazor-grid%})