public bool Exists <T>(Expression <Func <T, bool> > condition) where T : class, new()
{
using (IExpressionCondition expression = db.GetExpressionCondition(condition))
{
string sql = $"SELECT 0 WHERE EXISTS(SELECT 0 FROM {typeof(T).GetTableName()} { expression.ToCondition(out DynamicParameters parameters)} );";
return(db.ExecuteScalar(CommandType.Text, sql, parameters) != null);
}
}
public int Delete <T>(Expression <Func <T, bool> > condition) where T : class, new()
{
using (IExpressionCondition expression = db.GetExpressionCondition(condition))
{
string sql = $"DELETE FROM [{typeof(T).GetTableName()}] { expression.ToCondition(out DynamicParameters parameters) }";
return(db.ExecuteNonQuery(CommandType.Text, sql, parameters));
}
}
public int Count <T>(Expression <Func <T, bool> > condition) where T : class, new()
{
using (IExpressionCondition expression = db.GetExpressionCondition(condition))
{
string sql = $"SELECT COUNT(0) FROM [{typeof(T).GetTableName()}] { expression.ToCondition(out DynamicParameters parameters)} ";
object value = db.ExecuteScalar(CommandType.Text, sql, parameters);
return(value == null ? 0 : (int)value);
}
}
public TValue ReadInfo <T, TValue>(Expression <Func <T, TValue> > field, Expression <Func <T, bool> > condition) where T : class, new()
{
using (IExpressionCondition expression = db.GetExpressionCondition(condition))
{
string conditionSql = expression.ToCondition(out DynamicParameters parameters);
string sql = $"SELECT { SchemaCache.GetColumnProperty(field).Name } FROM {typeof(T).GetTableName()} {conditionSql} LIMIT 0,1;";
object value = db.ExecuteScalar(CommandType.Text, sql, parameters);
if (value == null)
{
return(default);
public IDataReader ReadData <T>(Expression <Func <T, bool> > condition, params Expression <Func <T, object> >[] fields) where T : class, new()
{
string field = string.Join(",", SchemaCache.GetColumns(fields).Select(t => $"{t.Name}"));
using (IExpressionCondition expression = db.GetExpressionCondition(condition))
{
string conditionSql = expression.ToCondition(out DynamicParameters parameters);
string sql = $"SELECT {field} FROM {typeof(T).GetTableName()} {conditionSql};";
return(db.ReadData(CommandType.Text, sql, parameters));
}
}
/// <summary>
/// 读取一个字段
/// </summary>
/// <typeparam name="T"></typeparam>
/// <typeparam name="TValue"></typeparam>
/// <param name="field"></param>
/// <param name="condition"></param>
/// <returns></returns>
public IEnumerable <TValue> ReadList <T, TValue>(Expression <Func <T, TValue> > field, Expression <Func <T, bool> > condition) where T : class, new()
{
string fieldName = SchemaCache.GetColumnProperty(field).Name;
List <TValue> list = new List <TValue>();
using (IExpressionCondition expression = db.GetExpressionCondition(condition))
{
string conditionSql = expression.ToCondition(out DynamicParameters parameters);
string sql = $"SELECT [{fieldName}] FROM [{typeof(T).GetTableName()}] {conditionSql}";
IDataReader reader = db.ReadData(CommandType.Text, sql, parameters);
while (reader.Read())
{
list.Add((TValue)reader[0]);
}
if (!reader.IsClosed)
{
reader.Close();
}
}
return(list);
}
