Programmatically modify MapTip Expression

Question

If I load a layer via a shapefile and set

((ILayer)myLayer).ShowTips = true; 

How can I change the tip content (I want to point it to a different column or have a expression of multiple columns) programatically with ArcEngine 10 and C#?

Answer 1

Take a look at the DisplayField on the IFeatureLayer for changing attribute field. For more advanced formating check out the IDisplayString and IDisplayExpressionProperties.

Made some code this work for me:

private void startMapTipsToolStripMenuItem_Click(object sender, EventArgs e)
        {
            ILayer layer = axMapControl1.Map.get_Layer(0);
            axMapControl1.ShowMapTips = true;
            IFeatureLayer fLayer = layer as IFeatureLayer;

            fLayer.ShowTips = true;
            fLayer.DisplayField = "AREANAME";

        }

        private void startMapTipsAdvancedToolStripMenuItem_Click(object sender, EventArgs e)
        {
            ILayer layer = axMapControl1.Map.get_Layer(0);
            axMapControl1.ShowMapTips = true;
            IFeatureLayer fLayer = layer as IFeatureLayer;

            fLayer.ShowTips = true;

            IDisplayString displayString = fLayer as IDisplayString;
            IDisplayExpressionProperties properties = displayString.ExpressionProperties;

            properties.Expression = "[AREANAME] & vbnewline & [POP2000]";
        }

Answer 2

ILayer.ShowTips Property: Indicates whether or not map tips are shown for the layer. If set to True, then map tips will be shown for the layer. You can determine the text that will be shown via TipText. For a FeatureLayer, this text comes from the data for IFeatureLayer::DisplayField.

In your case that would be a simple

((IFeatureLayer)myLayer).DisplayField = "colName";