C# MapX 圖層動態建立：從資料庫讀取資料生成點圖層完整流程

本文整理自網路文章《MapX從資料庫讀取資料形成新圖層（C#）》，解決兩大問題：

1. MapX 從資料庫建立新圖層
2. ADO.NET DataTable 轉 COM ADODB.Recordset (MapX 僅支援 ADO)

DataTable → Recordset 轉換器

using ADODB;
using System.Data;

public sealed class AdoNetToAdo
{
    public static Recordset ConvertDataTableToRecordset(DataTable table)
    {
        var rs = new RecordsetClass();
        // 1. 建立欄位對應
        foreach (DataColumn dc in table.Columns)
            rs.Fields.Append(dc.ColumnName, GetAdoType(dc.DataType), -1, FieldAttributeEnum.adFldIsNullable, Missing.Value);

        rs.Open(Missing.Value, Missing.Value, CursorTypeEnum.adOpenUnspecified, LockTypeEnum.adLockUnspecified, -1);

        // 2. 逐列填入資料
        foreach (DataRow dr in table.Rows)
        {
            rs.AddNew(Missing.Value, Missing.Value);
            for (int i = 0; i < table.Columns.Count; i++)
                rs.Fields[i].Value = dr[i];
        }
        return rs;
    }

    private static DataTypeEnum GetAdoType(Type netType) => netType.ToString() switch
    {
        "System.Boolean" => DataTypeEnum.adBoolean,
        "System.Byte" => DataTypeEnum.adUnsignedTinyInt,
        "System.Char" => DataTypeEnum.adChar,
        "System.DateTime" => DataTypeEnum.adDate,
        "System.Decimal" => DataTypeEnum.adDecimal,
        "System.Double" => DataTypeEnum.adDouble,
        "System.Int16" => DataTypeEnum.adSmallInt,
        "System.Int32" => DataTypeEnum.adInteger,
        "System.Int64" => DataTypeEnum.adBigInt,
        "System.SByte" => DataTypeEnum.adTinyInt,
        "System.Single" => DataTypeEnum.adSingle,
        "System.String" => DataTypeEnum.adVarChar,
        "System.UInt16" => DataTypeEnum.adUnsignedSmallInt,
        "System.UInt32" => DataTypeEnum.adUnsignedInt,
        "System.UInt64" => DataTypeEnum.adUnsignedBigInt,
        _ => throw new Exception($"無對應 ADO 型別: {netType}")
    };
}

建立 MapX 點圖層完整流程

private void DeleteLayerByName(string name)
{
    for (int i = 1; i <= axMap1.Layers.Count; i++)
        if (axMap1.Layers[i].Name == name) { axMap1.Layers.Remove(i); break; }
}

private void CreateLayerFromDB(string layerName, Recordset rs)
{
    DeleteLayerByName(layerName);

    // 1. 定義欄位結構
    var flds = new MapXLib.FieldsClass();
    flds.Add("stationid", "theid", MapXLib.AggregationFunctionConstants.miAggregationIndividual, MapXLib.FieldTypeConstants.miTypeString);
    flds.Add("address", "address", MapXLib.AggregationFunctionConstants.miAggregationIndividual, MapXLib.FieldTypeConstants.miTypeString);
    flds.Add("longitude", "longitude", MapXLib.AggregationFunctionConstants.miAggregationSum, MapXLib.FieldTypeConstants.miTypeNumeric); // 經度
    flds.Add("latitude", "latitude", MapXLib.AggregationFunctionConstants.miAggregationSum, MapXLib.FieldTypeConstants.miTypeNumeric);   // 緯度

    // 2. 定義繫結圖層：XY 模式，指定經緯度欄位索引 (1-based)
    var bindLayer = new MapXLib.BindLayerClass
    {
        LayerName = layerName,
        RefColumn1 = 3,  // longitude
        RefColumn2 = 4,  // latitude
        LayerType = MapXLib.BindLayerTypeConstants.miBindLayerTypeXY
    };

    // 3. 加入 DataSet → 自動產生圖層
    var ds = axMap1.DataSets.Add(
        MapXLib.DatasetTypeConstants.miDataSetADO, rs, layerName,
        "stationid", "address", bindLayer, flds, false);

    // 4. 設定顯示風格：點位圖示
    var layer = axMap1.Layers._Item(layerName);
    layer.OverrideStyle = true;
    const string icon = "icon.bmp"; // 需放於 MapX 安裝目錄 CUSTSYMB 資料夾
    if (layer.Style.SupportsBitmapSymbols)
    {
        layer.Style.SymbolType = MapXLib.SymbolTypeConstants.miSymbolTypeBitmap;
        layer.Style.SymbolBitmapSize = 60;
        layer.Style.SymbolBitmapTransparent = true;
        layer.Style.SymbolBitmapName = icon;
    }
}

關鍵點總結

• BindLayer.RefColumn1/2 為 1-based 索引，對應 Fields.Add 順序
• miBindLayerTypeXY 表示以經緯度直接定位，無需幾何欄位
• 圖示檔 (.bmp) 須置於 MapX CUSTSYMB 目錄
• 先刪除同名圖層避免重複