---
id: "P:cAlgo.API.ChartMouseEventArgs.BarIndex"
kind: "property"
type: "T:cAlgo.API.ChartMouseEventArgs"
url: "https://help.ctrader.com/ctrader-algo/references/EventArgs/ChartMouseEventArgs/BarIndex/"
---

> Documentation index for agents: https://help.ctrader.com/ctrader-algo/llms.txt · machine index: https://help.ctrader.com/ctrader-algo/api.json

# ChartMouseEventArgs.BarIndex

Member of [ChartMouseEventArgs](https://help.ctrader.com/ctrader-algo/references/EventArgs/ChartMouseEventArgs/index.md).

## BarIndex

Gets the exact bar index of the mouse event.

Environments: Desktop supported · CLI not supported · Cloud not supported.

- CLI: Never raised in the CLI: the events that pass it never fire there (ChartArea.MouseDown, ChartArea.MouseEnter, ChartArea.MouseLeave and more).
- Cloud: Never raised in the cloud: the events that pass it never fire there (ChartArea.MouseDown, ChartArea.MouseEnter, ChartArea.MouseLeave and more).

C#:

```csharp
public double BarIndex {get;}
```

Python:

```python
chartMouseEventArgs.BarIndex: float
```

### Returns

`double` — 

### Examples

C#:

```csharp
protected override void OnStart()
{
    Chart.MouseDown += OnChartMouseDown;
}

private void OnChartMouseDown(ChartMouseEventArgs args)
{
    var barIndex = (int)Math.Round(args.BarIndex);
    Chart.DrawVerticalLine("clickedBar", barIndex, Color.Yellow);
    Print("Exact bar index: {0}, nearest bar: {1}", args.BarIndex, barIndex);
}
```

Python:

```python
def on_start(self):
    api.Chart.MouseDown += self.on_chart_mouse_down

def on_chart_mouse_down(self, args):
    bar_index = int(round(args.BarIndex))
    api.Chart.DrawVerticalLine("clickedBar", bar_index, Color.Yellow)
    api.Print(f"Exact bar index: {args.BarIndex}, nearest bar: {bar_index}")
```