/// <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);
}
}
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 static TValue ExecuteScalar <T, TValue>(this DbExecutor db, T obj) where T : IProcedureModel
{
object result = db.ExecuteScalar(CommandType.StoredProcedure, typeof(T).Name, obj.ToParameters());
if (result == null)
{
return(default);
public void ExecuteScalar()
{
using (var exec = new DbExecutor(connectionFactory()))
{
exec.ExecuteScalar <long>("select @TypeId", new { TypeId = 2 })
.Is(2);
exec.ExecuteScalar <object>("select null").Is(DBNull.Value);
}
DbExecutor.ExecuteScalar <string>(connectionFactory(), "select date('now')")
.Is(DateTime.Now.ToString("yyyy-MM-dd"));
DbExecutor.ExecuteScalar <object>(connectionFactory(), "select null")
.Is(DBNull.Value);
}
public void ExecuteScalar()
{
using (var exec = new DbExecutor(connectionFactory()))
{
exec.ExecuteScalar <int>("select max(TypeId) from Types where TypeId <= @TypeId", new { TypeId = 2 })
.Is(2);
exec.ExecuteScalar <int?>("select TypeId from Types where TypeId = -1000")
.IsNull();
}
DbExecutor.ExecuteScalar <DateTime>(connectionFactory(), "select GETDATE()")
.Day.Is(DateTime.Now.Day);
DbExecutor.ExecuteScalar <int?>(connectionFactory(), "select TypeId from Types where TypeId = -1000")
.IsNull();
}
/// <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);