特別說(shuō)明,本文整理自一篇網(wǎng)絡(luò)的文章《MapX從數(shù)據(jù)庫(kù)讀取數(shù)據(jù)形成新圖層(C#)》
在C#中實(shí)現(xiàn)MapX從數(shù)據(jù)庫(kù)讀取數(shù)據(jù)形成新圖層分為兩個(gè)問(wèn)題:
1. MapX從數(shù)據(jù)庫(kù)讀取數(shù)據(jù)形成新圖層;
2. 將DataTable轉(zhuǎn)換為ADO的Recordset。這里的第二個(gè)問(wèn)題是由第一個(gè)問(wèn)題引起的,因?yàn)镸apX是一個(gè)COM控件,而且它只支持ADO的數(shù)據(jù)訪問(wèn)方式,而C#編程時(shí)一般會(huì)使用ADO.NET方式,為此需要在兩種方式之間做一下轉(zhuǎn)換。(當(dāng)然也可以在C#中使用ADO方式)
DataTable轉(zhuǎn)換為ADO的Recordset的操作代碼如下所示。
/// <summary>
/// 在.net中用ADO.NET取代了ADO實(shí)現(xiàn)對(duì)數(shù)據(jù)的訪問(wèn),但一些COM控件只支持ADO并不支持ADO.NET。
/// 為了使用這類(lèi)控件,只能將ADO.NET中的數(shù)據(jù)對(duì)象,比如轉(zhuǎn)換DataTable為ADO中的Recordset
/// (DataSet對(duì)象本質(zhì)上是DataTable的集合,因此本文只講述DataTable對(duì)象的轉(zhuǎn)換)。
/// </summary>
public sealed class ADONETtoADO
{
/// <summary>
/// 將DataTable對(duì)象轉(zhuǎn)換為Recordeset對(duì)象
/// </summary>
/// <param name="table">DataTable對(duì)象</param>
/// <returns>轉(zhuǎn)換后得到的Recordeset對(duì)象</returns>
public static Recordset ConvertDataTableToRecordset(DataTable table)
{
//思路:
// 1. 創(chuàng)建Recordset對(duì)象后,在其中對(duì)應(yīng)DataTable的Column創(chuàng)建Field,為此需要將ADO.NET的數(shù)據(jù)類(lèi)型轉(zhuǎn)換為ADO的數(shù)據(jù)類(lèi)型;
// 2. 打開(kāi)Recordset對(duì)象,對(duì)應(yīng)DataTable對(duì)象中的每一行,在Recordset對(duì)象中新建一條記錄,并對(duì)每個(gè)字段賦值。
Recordset rs = new RecordsetClass();
foreach (DataColumn dc in table.Columns)
{
rs.Fields.Append(dc.ColumnName, GetDataType(dc.DataType), -1, FieldAttributeEnum.adFldIsNullable, Missing.Value);
}
rs.Open(Missing.Value, Missing.Value, CursorTypeEnum.adOpenUnspecified, LockTypeEnum.adLockUnspecified, -1);
foreach (DataRow dr in table.Rows)
{
rs.AddNew(Missing.Value, Missing.Value); object o;
for (int i = 0; i < table.Columns.Count; i++)
{
rs.Fields[i].Value = dr[i];
o = rs.Fields[i].Value;
}
}
return rs;
}
/// <summary>
/// 將ADO.NET的數(shù)據(jù)類(lèi)型轉(zhuǎn)換為ADO的數(shù)據(jù)類(lèi)型
/// </summary>
/// <param name="dataType">ADO.NET的數(shù)據(jù)類(lèi)型</param>
/// <returns>ADO的數(shù)據(jù)類(lèi)型</returns>
private static DataTypeEnum GetDataType(Type dataType)
{
switch (dataType.ToString())
{
case "System.Boolean": return DataTypeEnum.adBoolean;
case "System.Byte": return DataTypeEnum.adUnsignedTinyInt;
case "System.Char": return DataTypeEnum.adChar;
case "System.DateTime": return DataTypeEnum.adDate;
case "System.Decimal": return DataTypeEnum.adDecimal;
case "System.Double": return DataTypeEnum.adDouble;
case "System.Int16": return DataTypeEnum.adSmallInt;
case "System.Int32": return DataTypeEnum.adInteger;
case "System.Int64": return DataTypeEnum.adBigInt;
case "System.SByte": return DataTypeEnum.adTinyInt;
case "System.Single": return DataTypeEnum.adSingle;
case "System.String": return DataTypeEnum.adVarChar;
//case "TimeSpan":return DataTypeEnum.
case "System.UInt16": return DataTypeEnum.adUnsignedSmallInt;
case "System.UInt32": return DataTypeEnum.adUnsignedInt;
case "System.UInt64": return DataTypeEnum.adUnsignedBigInt;
default: throw (new Exception("沒(méi)有對(duì)應(yīng)的數(shù)據(jù)類(lèi)型"));
}
}
}
在得到了Recordset對(duì)象后,如何解決第一個(gè)問(wèn)題。步驟如下:
1. 創(chuàng)建CMapXFields對(duì)象,并對(duì)應(yīng)數(shù)據(jù)庫(kù)中字段添加字段;
2. 創(chuàng)建CMapXBindLayer對(duì)象,指定其坐標(biāo)值字段的序號(hào);
3. 向map.DataSets中添加數(shù)據(jù)集,從而生成新的圖層;
4. 指定新圖層中要素的顯示風(fēng)格,本文采用顯示位圖的方式,為此需要將要顯示的位圖放入MapX安裝目錄的CUSTSYMB文件夾下。
具體的操作代碼如下所示:
/// <summary>
/// 刪除所有的圖層數(shù)據(jù)
/// </summary>
/// <param name="layerName"></param>
private void DeleteLayerByName(string layerName)
{
//Layer的序號(hào)是從1開(kāi)始
int count = axMap1.Layers.Count;
for (int i = 1; i < count; i++)
{
if (axMap1.Layers[i].Name == layerName)
{
axMap1.Layers.Remove(i);
}
}
}
/// <summary>
/// 創(chuàng)建新的圖層信息
/// </summary>
/// <param name="layerName"></param>
/// <param name="rsNoPass"></param>
private void CreatNewLayerfromDB(string layerName, ADODB.Recordset rsNoPass)
{
DeleteLayerByName(layerName); //將原有層刪除
CMapXFields flds = new FieldsClass();
// Describe the structure of the Unbound dataset
flds.Add("stationid", "theid", AggregationFunctionConstants.miAggregationIndividual,
FieldTypeConstants.miTypeString);
flds.Add("address", "address", AggregationFunctionConstants.miAggregationIndividual,
FieldTypeConstants.miTypeString);
flds.Add("longitude", "longitude", AggregationFunctionConstants.miAggregationSum,
FieldTypeConstants.miTypeNumeric); //經(jīng)度
flds.Add("latitude", "latitude", AggregationFunctionConstants.miAggregationSum,
FieldTypeConstants.miTypeNumeric); //緯度
CMapXBindLayer bindLayerObject = new BindLayerClass();
bindLayerObject.LayerName = layerName;
bindLayerObject.RefColumn1 = 3;
bindLayerObject.RefColumn2 = 4;
bindLayerObject.LayerType = BindLayerTypeConstants.miBindLayerTypeXY;
CMapXDataset dataSet = axMap1.DataSets.Add(DatasetTypeConstants.miDataSetADO, rsNoPass, layerName, "stationid", "address", bindLayerObject, flds, false);
CMapXLayer layer = axMap1.Layers._Item(layerName);
layer.OverrideStyle = true;
string picName = "icon.BMP";
if (layer.Style.SupportsBitmapSymbols == true)
{
layer.Style.SymbolType = SymbolTypeConstants.miSymbolTypeBitmap;
layer.Style.SymbolBitmapSize = 60;
layer.Style.SymbolBitmapTransparent = true;
layer.Style.SymbolBitmapName = picName;
}
}