/// <summary>
/// 包含字符串的表达式 “IsNullOrEmpty | IsNullOrWhiteSpace”.
/// </summary>
/// <param name="expression">表达式.</param>
/// <returns>结果.</returns>
protected virtual object VisitIsNullExpression(MethodCallExpression expression)
{
object column = null;
if (expression.Object != null)
{
column = VisitExpression(expression.Object);
}
else
{
column = new BaseExpressionVisitor().Visit(expression.Arguments[0]);
}
object value = null;
if (expression.Arguments.Count > 0)
{
value = VisitExpression(expression.Arguments[0]);
}
return($"({value} IS NULL OR {value} = '' OR LEN({value}) <= 0)");
}
/// <summary>
/// 包含字符串的表达式 “ToSting ”.
/// </summary>
/// <param name="expression">表达式.</param>
/// <param name="textSearch">类型.</param>
/// <returns>结果.</returns>
protected virtual object VisitTostingExpression(MethodCallExpression expression, TextSearch textSearch)
{
//column()
object column = null;
if (expression.Object != null)
{
column = VisitExpression(expression.Object);
}
else
{
column = new BaseExpressionVisitor().Visit(expression.Arguments[0]);
}
//(value)
object value = null;
if (expression.Arguments.Count > 0)
{
value = VisitExpression(expression.Arguments[0]);
}
var textSQL = string.Empty;
switch (textSearch)
{
case TextSearch.ToString:
if (value != null)
{
//.ToString("yyyy") | .ToString("yyyyMMdd") ...
if (typeof(TEntity).GetField(value.ToString()) == null && typeof(TEntity).GetProperty(value.ToString()) == null)
{
switch (value.ToString())
{
case "yyyy":
textSQL = $"CONVERT(VARCHAR(4), {column} , 23)"; //2020
break;
case "MM-dd":
textSQL = $"CONVERT(VARCHAR(5), {column} , 10)"; //05-08
break;
case "yyyMMdd":
textSQL = $"CONVERT(VARCHAR(100), {column} , 112)"; //20200508
break;
case "yyyy-MM-dd":
textSQL = $"CONVERT(VARCHAR(100), {column} , 23)"; //2020-05-08
break;
case "yyyy-MM-dd hh:mm:ss":
textSQL = $"CONVERT(VARCHAR(100), {column} , 20)"; //2020-05-08 12:20:22
break;
case "MMdd":
textSQL = $"SUBSTRING(CONVERT(VARCHAR(100), {column} , 112),5,10 - 5)"; //0508
break;
default:
throw new Exception("时间格式错误或暂不支持。");
}
}
}
else if (column != null)
{
//.ToString()
if (typeof(TEntity).GetField(column.ToString()) != null || typeof(TEntity).GetProperty(column.ToString()) != null)
{
//列名
textSQL = $"CAST({column} AS VARCHAR(MAX))";
}
else if (typeof(TEntity).GetField(column.ToString()) == null && typeof(TEntity).GetProperty(column.ToString()) == null)
{
//非列名
textSQL = $"CAST('{column}' AS VARCHAR(MAX))";
}
}
else
{
throw new Exception("“ToString”解析失败。");
}
return(textSQL);
case TextSearch.Trim:
if (typeof(TEntity).GetField(column.ToString()) != null || typeof(TEntity).GetProperty(column.ToString()) != null)
{
textSQL = $"LTRIM(RTRIM({column}))";
}
else
{
textSQL = $"LTRIM(RTRIM('{column}'))";
}
return(textSQL);
case TextSearch.ToDateTime:
if (value != null)
{
if (typeof(TEntity).GetField(value.ToString()) != null ||
typeof(TEntity).GetProperty(value.ToString()) != null)
{
textSQL = $"CAST({value} AS DATETIME)";
}
}
return(textSQL);
default:
throw new ArgumentOutOfRangeException($"Invalid TextSearch value '{textSearch}'.", nameof(textSearch));
}
}
