【IT168 技术文档】在C#中实现MapX从数据库读取数据形成新图层分为两个问题：
1. MapX从数据库读取数据形成新图层;
2. 将DataTable转换为ADO的Recordset。这里的第二个问题是由第一个问题引起的，因为MapX是一个COM控件，而且它只支持ADO的数据访问方式，而C#编程时一般会使用ADO.NET方式，为此需要在两种方式之间做一下转换。(当然也可以在C#中使用ADO方式)
DataTable转换为ADO的Recordset的操作代码如下所示。
/// <summary>
/// 在.net中用ADO.NET取代了ADO实现对数据的访问，但一些COM控件只支持ADO并不支持ADO.NET。
/// 为了使用这类控件，只能将ADO.NET中的数据对象，比如转换DataTable为ADO中的Recordset
/// (DataSet对象本质上是DataTable的集合，因此本文只讲述DataTable对象的转换)。
/// <summary>
public sealed class ADONETtoADO
{
/// <summary>
/// 将DataTable对象转换为Recordeset对象
/// <summary>
/// DataTable对象
/// 转换后得到的Recordeset对象
public static Recordset ConvertDataTableToRecordset(DataTable table)
{
//思路：
// 1. 创建Recordset对象后，在其中对应DataTable的Column创建Field，为此需要将ADO.NET的数据类型转换为ADO的数据类型;
// 2. 打开Recordset对象，对应DataTable对象中的每一行，在Recordset对象中新建一条记录，并对每个字段赋值。
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>
/// 将ADO.NET的数据类型转换为ADO的数据类型
/// <summary>
/// ADO.NET的数据类型
/// ADO的数据类型
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("没有对应的数据类型"));
}
}
}
/// 在.net中用ADO.NET取代了ADO实现对数据的访问，但一些COM控件只支持ADO并不支持ADO.NET。
/// 为了使用这类控件，只能将ADO.NET中的数据对象，比如转换DataTable为ADO中的Recordset
/// (DataSet对象本质上是DataTable的集合，因此本文只讲述DataTable对象的转换)。
/// <summary>
public sealed class ADONETtoADO
{
/// <summary>
/// 将DataTable对象转换为Recordeset对象
/// <summary>
/// DataTable对象
/// 转换后得到的Recordeset对象
public static Recordset ConvertDataTableToRecordset(DataTable table)
{
//思路：
// 1. 创建Recordset对象后，在其中对应DataTable的Column创建Field，为此需要将ADO.NET的数据类型转换为ADO的数据类型;
// 2. 打开Recordset对象，对应DataTable对象中的每一行，在Recordset对象中新建一条记录，并对每个字段赋值。
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>
/// 将ADO.NET的数据类型转换为ADO的数据类型
/// <summary>
/// ADO.NET的数据类型
/// ADO的数据类型
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("没有对应的数据类型"));
}
}
}
在得到了Recordset对象后，如何解决第一个问题。步骤如下：
1. 创建CMapXFields对象，并对应数据库中字段添加字段;
2. 创建CMapXBindLayer对象，指定其坐标值字段的序号;
3. 向map.DataSets中添加数据集，从而生成新的图层;
4. 指定新图层中要素的显示风格，本文采用显示位图的方式，为此需要将要显示的位图放入MapX安装目录的CUSTSYMB文件夹下。
具体的操作代码如下所示：
/// <summary>
/// 删除所有的图层数据
/// <summary>
/// <param name="layerName"></param>
private void DeleteLayerByName(string layerName)
{
//Layer的序号是从1开始
int count = axMap1.Layers.Count;
for (int i = 1; i < count; i++)
{
if (axMap1.Layers[i].Name == layerName)
{
axMap1.Layers.Remove(i);
}
}
}
/// <summary>
/// 创建新的图层信息
/// <summary>
/// <param name="layerName"></param>
/// <param name="rsNoPass"></param>
private void CreatNewLayerfromDB(string layerName, ADODB.Recordset rsNoPass)
{
DeleteLayerByName(layerName); //将原有层删除
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); //经度
flds.Add("latitude", "latitude", AggregationFunctionConstants.miAggregationSum,
FieldTypeConstants.miTypeNumeric); //纬度
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;
}
}
/// 删除所有的图层数据
/// <summary>
/// <param name="layerName"></param>
private void DeleteLayerByName(string layerName)
{
//Layer的序号是从1开始
int count = axMap1.Layers.Count;
for (int i = 1; i < count; i++)
{
if (axMap1.Layers[i].Name == layerName)
{
axMap1.Layers.Remove(i);
}
}
}
/// <summary>
/// 创建新的图层信息
/// <summary>
/// <param name="layerName"></param>
/// <param name="rsNoPass"></param>
private void CreatNewLayerfromDB(string layerName, ADODB.Recordset rsNoPass)
{
DeleteLayerByName(layerName); //将原有层删除
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); //经度
flds.Add("latitude", "latitude", AggregationFunctionConstants.miAggregationSum,
FieldTypeConstants.miTypeNumeric); //纬度
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;
}
}
