# Compare CSV Files

> The example below explains how to create two new `.csv` files that store the similarities and the differences between two existing `.csv` files. It presents activities such as [Read CSV](https://docs.uipath.com/activities/other/latest/productivity/read-csv-file) or [Build Data Table](https://docs.uipath.com/activities/other/latest/user-guide/build-data-table). You can find these activities in the **UiPath.Excel.Activities** package.

The example below explains how to create two new `.csv` files that store the similarities and the differences between two existing `.csv` files. It presents activities such as [Read CSV](https://docs.uipath.com/activities/other/latest/productivity/read-csv-file) or [Build Data Table](https://docs.uipath.com/activities/other/latest/user-guide/build-data-table). You can find these activities in the **UiPath.Excel.Activities** package.

## Create a new CSV file with the differences between two tables

This is how the automation process can be built:

1. Open Studio and create a new **Process** and name it **Differences**.
   :::note
Make sure to add the `.csv` files that you want to use in the project folder. You can also use the files we provided by downloading the example available at the bottom of this page.
   :::
2. Drag a **Flowchart** container in the **Workflow Designer**.
   * Create the following variables:

   | Variable Name | Variable Type | Default Value |
   | --- | --- | --- |
   | `Data1` | **System.Data.DataTable** | **N/A** |
   | `Data2` | **System.Data.DataTable** | **N/A** |
   | `newRow` | **System.Data.DataTable** | **N/A** |
3. Place a **Read CSV** activity in the **Flowchart** panel.
   * Open the context menu for the **Read CSV** activity and select the **Set as Start Node** option.
   * In the **Properties** panel, add the path of the `csv1.csv` file in the **FilePath** field.
   * Select the **IncludeColumnName** check box.
   * Add the variable `Data1` in the **DataTable** field.
4. Add a new **Read CSV** activity and connect it to the previous one.
   * In the **Properties** panel, add the path of the `csv2.csv` file in the **FilePath** field.
   * Select the **IncludeColumnName** check box.
   * Add the variable `Data2` in the **DataTable** field.
5. Drag a **Sequence** container and connect it to the previous **Read CSV** activity.
6. Open the **Sequence**.
7. Drag a **Build Data Table** activity to the **Sequence**.
   * In the **Properties** panel, add the variable `newRow` in the **DataTable** field.
   * Select the **DataTable** button, inside the body of the **Build Data Table** activity. The **Build Data Table** window contains a table with two columns and rows.
   * On the left column, select the **Edit Column** button and add the name `Number` in the **ColumnName** field.
   * Set the **Data Type** as **Int32**.
   * Select the **OK** option for closing the window.
   * On the right column, select the **Edit Column** button and add the name `Character` in the **ColumnName** field.
   * Set the **Data Type** as **String**.
   * Select the **OK** option for closing the window.
   * Select the **OK** button again to close the window.
8. Drag a **For Each Row** activity under the **Build Data Table** activity.
   * In the **Properties** panel, add the variable `Data1` in the **DataTable** field.
   * Select the **Body** sequence and create the following variables:

   | Variable Name | Variable Type | Default Value |
   | --- | --- | --- |
   | `strCurrentNo` | **String** | **N/A** |
   | `selectedRow` | **IEnumerable<DataRow>** | **N/A** |
9. Place an **Assign** activity in the body of the **For Each Row** activity.
   * Add the variable `strCurrentNo` in the **To** field.
   * In the **Properties** panel, add the expression `row("Number").ToString` in the **Value** field.
10. Drag another **Assign** activity and place it under the previous one.
    * Add the variable `selectedRow` in the **To** field.
    * In the **Properties** panel, add the expression `Data2.Select("Number ="+strCurrentNo)` in the **Value** field. The `Select(String)` method is used to filter and extract the values that are equal in the two `.csv` files.
11. Place an **If** activity below the last **Assign** activity.
    * Add the expression `drSelectedRows is Nothing or drSelectedRows.Count=0` in the **Condition** field. This condition checks if the `selectedRow` variable is invalid or if the number of rows is 0.
12. Drag an **Add Data Row** activity to the **Then** section of the **If** activity.
    * In the **Properties** panel, add the expression `row.ItemArray` in the **ArrayRow** field and the variable `newRow` in the **DataTable** field.
13. Return to the **Flowchart**.
14. Drag a **Write CSV** activity under the **Sequence** container and connect it to it.

* Enter a name for the file to be created in the **FilePath** field. In this case, the input is `“Differences.csv”`.
* Add the variable `newRow` in the **DataTable** field.
* Select the **AddHeaders** check box for considering the first row as headers.

## Create a new CSV file with the similarities between two tables

This is how the automation process can be built:

1. Repeat steps 1-10 from the **Differences** flowchart.
2. The new **Flowchart** should be named **Similarities**.
3. Drag an **Add Data Row** under the two **Assign** activities.
   * In the **Properties** panel, add the value `row.ItemArray` in the **ArrayRow** field and the variable `newRow` in the **DataTable** field.
4. Return to the **Flowchart**.
5. Drag a **Write CSV** activity under the **Sequence** container and connect it to it.
   * Enter a name for the file to be created in the **FilePath** field. In this case, the input is `“Similarities.csv”`.
   * Add the variable `newRow` in the **DataTable** field.
   * Select the **AddHeaders** check box for considering the first row as headers.
6. Save the automation project.
7. Run the process. The automation process should filter the data and create two new files, one with the differences and one with the similarities between the two initial files.

[Download example](https://docexamples.uipath.com/examples/Activities/Comparing%20CSV%20files.zip)