/// <summary>
/// 数据是否存在
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="condition"></param>
/// <returns></returns>
public bool Exists <T>(Expression <Func <T, bool> > condition) where T : class, new()
{
using (ExpressionCondition expression = db.GetExpressionCondition(condition))
{
string sql = $"SELECT 0 WHERE EXISTS(SELECT 0 FROM [{typeof(T).GetTableName()}] { expression.ToCondition(out DynamicParameters parameters)} )";
object value = db.ExecuteScalar(CommandType.Text, sql, parameters);
return(value != null);
}
}
/// <summary>
/// 查询一个值
/// </summary>
public TValue ReadInfo <T, TValue>(Expression <Func <T, TValue> > field, Expression <Func <T, bool> > condition) where T : class, new()
{
using (ExpressionCondition expression = db.GetExpressionCondition(condition))
{
string conditionSql = expression.ToCondition(out DynamicParameters parameters);
string sql = $"SELECT TOP 1 { SchemaCache.GetColumnProperty(field).Name } FROM [{typeof(T).GetTableName()}] {conditionSql}";
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 (ExpressionCondition 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>
/// 查询一个值
/// </summary>
/// <typeparam name="T"></typeparam>
/// <typeparam name="TValue"></typeparam>
/// <param name="field"></param>
/// <param name="condition"></param>
/// <returns></returns>
public static TValue ExecuteScalar <T, TValue>(this DbExecutor db, Expression <Func <T, TValue> > field, Expression <Func <T, bool> > condition) where T : class
{
using (ExpressionCondition expression = new ExpressionCondition())
{
expression.Visit(field);
string sql = $"SELECT TOP 1 {expression.ToString()} FROM [{typeof(T).GetTableName()}]";
expression.Visit(condition);
sql += expression.ToCondition(out DynamicParameters parameters);
object value = db.ExecuteScalar(CommandType.Text, sql, parameters);
if (value == null)
{
return(default);
private IExpressionBuilder Add(string key, ExpressionCondition expressionCondition, ExpressionComparer?expressionComparer, object value = null)
{
expressionParameterDictionary.Add(key, new ExpressionParameter
{
Name = key,
Value = value,
Condition = expressionCondition,
ExpressionComparer = expressionComparer ?? ExpressionComparer.Equal
});
return(this);
}
/// <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 (ExpressionCondition 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);
}
