有谁知道在运行时基于DataTable
的架构创建SQL Server CE(Compact 3.5)表的最佳方式吗?我不想根据所有不同的可能数据类型制定CREATE TABLE
声明等。以编程方式从DataTable创建SQL Server CE表
作为一个奖励 - 你知道如何直接从数据表中填写它吗?
有谁知道在运行时基于DataTable
的架构创建SQL Server CE(Compact 3.5)表的最佳方式吗?我不想根据所有不同的可能数据类型制定CREATE TABLE
声明等。以编程方式从DataTable创建SQL Server CE表
作为一个奖励 - 你知道如何直接从数据表中填写它吗?
我编写了一个合理的解决方案,但希望避免对SQL类型case语句:
首先一个巧妙的方法来从.NET类型转换为SqlDBType:
/// <summary>
/// Gets the correct SqlDBType for a given .NET type. Useful for working with SQL CE.
/// </summary>
/// <param name="type">The .Net Type used to find the SqlDBType.</param>
/// <returns>The correct SqlDbType for the .Net type passed in.</returns>
public static SqlDbType GetSqlDBTypeFromType(Type type)
{
TypeConverter tc = TypeDescriptor.GetConverter(typeof(DbType));
if (/*tc.CanConvertFrom(type)*/ true)
{
DbType dbType = (DbType)tc.ConvertFrom(type.Name);
// A cheat, but the parameter class knows how to map between DbType and SqlDBType.
SqlParameter param = new SqlParameter();
param.DbType = dbType;
return param.SqlDbType; // The parameter class did the conversion for us!!
}
else
{
throw new Exception("Cannot get SqlDbType from: " + type.Name);
}
}
的情况声明的类型使用SQL语句:
/// <summary>
/// The method gets the SQL CE type name for use in SQL Statements such as CREATE TABLE
/// </summary>
/// <param name="dbType">The SqlDbType to get the type name for</param>
/// <param name="size">The size where applicable e.g. to create a nchar(n) type where n is the size passed in.</param>
/// <returns>The SQL CE compatible type for use in SQL Statements</returns>
public static string GetSqlServerCETypeName(SqlDbType dbType, int size)
{
// Conversions according to: http://msdn.microsoft.com/en-us/library/ms173018.aspx
bool max = (size == int.MaxValue) ? true : false;
bool over4k = (size > 4000) ? true : false;
switch (dbType)
{
case SqlDbType.BigInt:
return "bigint";
case SqlDbType.Binary:
return string.Format("binary ({0})", size);
case SqlDbType.Bit:
return "bit";
case SqlDbType.Char:
if (over4k) return "ntext";
else return string.Format("nchar({0})", size);
ETC...
后来终于CREATE TABLE语句:
/// <summary>
/// Genenerates a SQL CE compatible CREATE TABLE statement based on a schema obtained from
/// a SqlDataReader or a SqlCeDataReader.
/// </summary>
/// <param name="tableName">The name of the table to be created.</param>
/// <param name="schema">The schema returned from reader.GetSchemaTable().</param>
/// <returns>The CREATE TABLE... Statement for the given schema.</returns>
public static string GetCreateTableStatement(string tableName, DataTable schema)
{
StringBuilder builder = new StringBuilder();
builder.Append(string.Format("CREATE TABLE [{0}] (\n", tableName));
foreach (DataRow row in schema.Rows)
{
string typeName = row["DataType"].ToString();
Type type = Type.GetType(typeName);
string name = (string)row["ColumnName"];
int size = (int)row["ColumnSize"];
SqlDbType dbType = GetSqlDBTypeFromType(type);
builder.Append(name);
builder.Append(" ");
builder.Append(GetSqlServerCETypeName(dbType, size));
builder.Append(", ");
}
if (schema.Rows.Count > 0) builder.Length = builder.Length - 2;
builder.Append("\n)");
return builder.ToString();
}
我已经使用和更新将代码从本·布林:
GetSqlDBTypeFromType
/// <summary>
/// Gets the correct SqlDBType for a given .NET type. Useful for working with SQL CE.
/// </summary>
/// <param name="type">The .Net Type used to find the SqlDBType.</param>
/// <returns>The correct SqlDbType for the .Net type passed in.</returns>
public static SqlDbType GetSqlDBTypeFromType(Type type)
{
TypeConverter tc = TypeDescriptor.GetConverter(typeof(DbType));
if (/*tc.CanConvertFrom(type)*/ true)
{
DbType dbType = (DbType)tc.ConvertFrom(type.Name);
// A cheat, but the parameter class knows how to map between DbType and SqlDBType.
SqlCeParameter param = new SqlCeParameter();
param.DbType = dbType;
return param.SqlDbType; // The parameter class did the conversion for us!!
}
else
{
throw new Exception("Cannot get SqlDbType from: " + type.Name);
}
}
GetSqlServerCETypeName
/// <summary>
/// The method gets the SQL CE type name for use in SQL Statements such as CREATE TABLE
/// </summary>
/// <param name="dbType">The SqlDbType to get the type name for</param>
/// <param name="size">The size where applicable e.g. to create a nchar(n) type where n is the size passed in.</param>
/// <returns>The SQL CE compatible type for use in SQL Statements</returns>
public static string GetSqlServerCETypeName(SqlDbType dbType, int size)
{
// Conversions according to: http://msdn.microsoft.com/en-us/library/ms173018.aspx
bool max = (size == int.MaxValue) ? true : false;
bool over4k = (size > 4000) ? true : false;
if (size>0)
{
return string.Format(Enum.GetName(typeof(SqlDbType), dbType)+" ({0})", size);
}
else
{
return Enum.GetName(typeof(SqlDbType), dbType);
}
}
GetCreateTableStatement
/// <summary>
/// Genenerates a SQL CE compatible CREATE TABLE statement based on a schema obtained from
/// a SqlDataReader or a SqlCeDataReader.
/// </summary>
/// <param name="tableName">The name of the table to be created.</param>
/// <param name="schema">The schema returned from reader.GetSchemaTable().</param>
/// <returns>The CREATE TABLE... Statement for the given schema.</returns>
public static string GetCreateTableStatement(DataTable table)
{
StringBuilder builder = new StringBuilder();
builder.Append(string.Format("CREATE TABLE [{0}] (", table.TableName));
foreach (DataColumn col in table.Columns)
{
SqlDbType dbType = GetSqlDBTypeFromType(col.DataType);
builder.Append("[");
builder.Append(col.ColumnName);
builder.Append("]");
builder.Append(" ");
builder.Append(GetSqlServerCETypeName(dbType, col.MaxLength));
builder.Append(", ");
}
if (table.Columns.Count > 0) builder.Length = builder.Length - 2;
builder.Append(")");
return builder.ToString();
}
CreateFromDataset
public static void CreateFromDataset(DataSet set, SqlCeConnection conn)
{
conn.Open();
SqlCeCommand cmd;
foreach (DataTable table in set.Tables)
{
string createSql = copyDB.GetCreateTableStatement(table);
Console.WriteLine(createSql);
cmd = new SqlCeCommand(createSql, conn);
Console.WriteLine(cmd.ExecuteNonQuery());
}
conn.Close();
}
}
不错!但是当你有一个空的DataTable或多行时,它不能正常工作。我用schema.Columns上的循环替换了“DataRow-foreach”-loop,并使用每列的ColumnName-和MaxLength-属性。 – Lars 2009-07-29 14:34:44