## RegisterAddInFunction(string, string, bool) {#registeraddinfunction}

Adds addin function into the workbook

```csharp
public int RegisterAddInFunction(string addInFile, string functionName, bool lib)
```

| Parameter | Type | Description |
| --- | --- | --- |
| addInFile | String | the file contains the addin functions |
| functionName | String | the addin function name |
| lib | Boolean | whether the given addin file is in the directory or sub-directory of Workbook Add-In library. This flag takes effect and makes difference when given addInFile is of relative path: true denotes the path is relative to Add-In library and false denotes the path is relative to this Workbook. |

### Return Value

ID of the data which contains given addin function

### Examples

```csharp
using System;
using System.IO;
using Aspose.Cells;

namespace AsposeCellsExamples
{
    public class WorksheetCollectionMethodRegisterAddInFunctionWithStringStringBooleanDemo
    {
        public static void Run()
        {
            // Create a new workbook
            Workbook wb = new Workbook();
            
            // Get the first worksheet
            Worksheet sheet = wb.Worksheets[0];
            
            // Set sample file paths (these would need to exist in your environment)
            string addInFile1 = Path.Combine("AddIns", "MyAddIn1.xlam");
            string addInFile2 = Path.Combine("AddIns", "MyAddIn2.xlam");
            
            // Register add-in functions with different parameters
            int id1 = wb.Worksheets.RegisterAddInFunction(addInFile1, "MY_UDF1", false);
            int id2 = wb.Worksheets.RegisterAddInFunction(addInFile2, "MY_UDF2", true);
            
            // Use the registered functions in cells
            sheet.Cells["A1"].Formula = "=MY_UDF1()";
            sheet.Cells["A2"].Formula = "=MY_UDF2()";
            
            // Save the workbook
            wb.Save("RegisterAddInFunctionDemo.xlsx", SaveFormat.Xlsx);
        }
    }
}
```

### See Also

* class [WorksheetCollection](../)
* namespace [Aspose.Cells](../../../aspose.cells/)
* assembly [Aspose.Cells](../../../)

---

## RegisterAddInFunction(int, string) {#registeraddinfunction_1}

Adds addin function into the workbook

```csharp
public string RegisterAddInFunction(int id, string functionName)
```

| Parameter | Type | Description |
| --- | --- | --- |
| id | Int32 | ID of the data which contains addin functions, can be got by the first call of `RegisterAddInFunction` for the same addin file. |
| functionName | String | the addin function name |

### Return Value

URL of the addin file which contains addin functions

### Examples

```csharp
using System;
using Aspose.Cells;

namespace AsposeCellsExamples
{
    public class WorksheetCollectionMethodRegisterAddInFunctionWithInt32StringDemo
    {
        public static void Run()
        {
            // Create a new workbook
            Workbook workbook = new Workbook();
            
            // Register first add-in function and get its ID
            int functionId = workbook.Worksheets.RegisterAddInFunction("externallink1.xlam", "customfunc1", false);
            
            // Register second add-in function using the same ID
            workbook.Worksheets.RegisterAddInFunction(functionId, "customfunc2");
            
            // Access the first worksheet
            Worksheet worksheet = workbook.Worksheets[0];
            Cells cells = worksheet.Cells;
            
            // Use the registered functions in formulas
            cells["A1"].Formula = "=customfunc1()";
            cells["A2"].Formula = "=customfunc2()";
            
            // Save the workbook
            workbook.Save("RegisterAddInFunctionDemo.xlsx");
        }
    }
}
```

### See Also

* class [WorksheetCollection](../)
* namespace [Aspose.Cells](../../../aspose.cells/)
* assembly [Aspose.Cells](../../../)